I also have Kiki on my reading list. I read the first couple of pages and apart from lacking furigana it doesn’t seem a massive step up from this book. Psychologically though it seems much harder with the denser text and longer pages.
I’m going to buy the audiobook as well, it’s quite a nice pace to listen to on the sample.
By the way have you seen the bookmeter website? It’s quite nice for keeping track of what you have read and are planning to read. There are quite a few Wanikani users with accounts and you can follow what others are reading.
It takes a bit of time to figure out the website and get set up, although that’s a good Japanese learning exercise in itself!
So you buy the audiobook to get the furigana 
I’m not sure what you mean by stack of conjugation but I think here we have two different clauses, both using なる. My guess is this 仕方がない here doesn’t only refer to him becoming interested but to the whole idea of him changing his name and identifying with the beetle. 
ひょろ長い体に真ん丸の目玉のオサムシは、自分に似ているように思えたのです。
One could think that the ground beetle, with its long thin body and its perfectly round eyeballs resembled him.
「そうだ、これから僕は、オサムシと名乗ろう。」
“Well, from now on, I will call myself Osamushi.”
それから治は、絵や漫画を描くときには、「手塚治虫」と、サインするようになったのです。
It’s from that moment on that Osamu (治）turned to sign his drawings and manga with “Osamu (治虫）Tezuka”.
I wondered how the Japanese give the pronunciation of their names:
ひょろ長い体に真ん丸の目玉のオサムシは、自分に似ているように思えたのです。
The osamushi, with its perfectly round eyeballs on its spindly body, seemed to be similar to himself.
「そうだ、これから僕は、オサムシと名乗ろう。」
“That’s it, from now on I will adopt Osamushi as my name.”
それから治は、絵や漫画を書くときには、「手塚治虫」とサインするようになったのです。
From then on when Osamu drew manga or drawings, he came to sign them “Osamu[shi] Tezuka”.
Seems like the pronunciations can be sort of arbitrary, and that’s why it’s common to put furigana on business cards. It would be easy to have a strange name this way I imagine, but also some interesting or unique ones.
I got a relative named “Mychal” (read: Michael), so parents can make very strange, arbitrary choices sometimes 
Better late than never. Thanks for the vocab sheet!
ひょろ長い体にまん丸の目玉のオサムシは、自分ににているように思えたのです。
Because he thought that ground beetle, with lanky body and perfectly round eyeballs, resembled himself.
「そうだ、これから僕は,オサムシと名乗ろう。」
“That’s right, I will call myself as Osamushi.”
それから治は、絵やまんがをかく時には、「手塚治虫」と、サインするようになったのです。
And then Osamu started signing pictures and manga as “Tezuka Osamu”.
I’m not sure but I think 思える comes from the potential form of 思う but is now it’s own verb with a slightly separate meaning. It’s something like „it seems to me“ (or to another individual).
治虫は、「将来は、漫画家か、昆虫の学者になりたいな。」と、考えていました。
Osamu thought: “In the future, I want to be a cartoonist or an entomologist.”
しかし、十五歳の時、その考えを変える事件がありました。
However, when he was fifteen, an incident happened that changed his mind.
両腕にバイキンが入り、もう少しで、両腕を切らなければならないほど、悪くなってしまったのです。
Bacteria infected both of his arms, and it became so bad that he almost had to have both of his arms amputated.
治虫はずいぶん長い間、病院に通いました。
Osamu went to the hospital for a very long time.
治虫は、「将来は、漫画家か、昆虫の学者になりたいな。」と、考えていました。
Osamu was thinking, “In the future, I want to become a manga author or an insect scholar.”
しかし、十五歳のとき、その考えを変える事件がありました。
However, when he was 15 years old there was an incident that changed that thinking.
両腕にバイキンが入り、もう少しで、両腕を切らなければならないほど、悪くなってしまったのです。
Bacteria had entered both his arms, and it got so bad that he almost had to have both arms cut off.
治虫はずいぶん長い間、病院に通いました。
For an awfully long period of time, Osamu went back and forth to the hospital
That second-to-last sentence confused me until I remembered that なければならない is a grammar point, and realized that もう少しで has it’s own Jisho entry.
治虫は、「将来は、漫画家か昆虫の学者になりたいな。」と、かんがえていました。
Osamu thought, “In the future, I want to be mangaka or insect researcher.”
しかし、十五歳の時、その考えを変える事件がありました。
However, when he was 15 years old, there was an incident that changed this thinking.
両腕にばいきんが入り、もう少しで、両腕を切らなければならないほど、わるくなってしまったのです。
Harmful bacteria infected both of his arms, requiring surgery, and after this his arms become very bad.
治虫はずいぶん長い間、病院に通いました。
Osamu spent awfully long time in the hospital.
If anyone could take a shot at doing break up analysis of this long sentence, would be great:
両腕にばいきんが入り、もう少しで、両腕を切らなければならないほど、わるくなってしまったのです。
I’ve started watching famous Cure Dolly playlist, and I guess determining what she calls “zero-ga” (omitted subject) is always a struggle for me. In the conversation, it is “I, me” by default. In the writing, it obviously not, so it may be the main character like Tezuka in this chapter, maybe not.
Sure 
First we have a bit of scene-setting:
両腕にばいきんが入り、- bacteria entered both his arms (ます-stem ending for continuation)
The main point of a sentence is always at the end, so let’s look there next:
わるくなってしまったのです。- unfortunately it became bad (this is 悪い + なる + てしまう + のです)
How bad did it get? That’s what is in between those two parts:
もう少しで、- almost もう少しで - Jisho.org
両腕を - both arms
切らなければならない - must cut off
ほど、- to the extent
So, all together: Bacteria entered both his arms, and that became bad to the extent of almost cutting off both his arms.
Note that this is a very literal translation, in natural English one would probably say something like “to the extent that his arms had to be cut off” or something, but in Japanese there is no passive voice being used here. This is a standard way of expressing things like these in Japanese: Although somebody else will do the action, it is still being expressed in active voice when it is clear that the action is performed by somebody else and not by the person themselves. (E.g. 髪を切った even when it was the hairdresser who did the cutting.)
Thanks Nicole, you’re always great at explaining!
To add to @NicoleIsEnough 's excellent explanation, I picked up a nice trick on how to read ほど from a book called Making Sense of Japanese.
Say you have the sentence:
泣きたいほど困った。
The part after ほど is “I was upset”.
Ask “How upset were you?”
The answer is in the ほど expression 泣きたい.
“I was so upset that I wanted to cry.” <—
I find this “so…that…” construction much easier to understand than translating ほど as “extent”. It’s more a grammar point than a vocab word.
Other examples:
[死ぬほど]のどがかわいている。
“I am thirsty.”
“How thirsty are you?”
“I’m so thirsty I could die.” <—
この仕事は[子供でもできるほど]優しいです。
“This job is easy.”
“How easy is this job?”
“This job is so easy that even a child could do it.” <—
The line in the book breaks down the same way:
[もう少しで、両腕を切らなければならないほど]、悪くなってしまったのです。
“It got bad”
“How bad did it get?”
“It got so bad that he almost had to have both arms cut off.”<—
Hope this isn’t too confusing…
Wow!
I guesshope at some point language constructs like that become intuitively clear. Definitely need to look for ほど usage nuances.
I always have to think of this book as well when I come across ほど. 
Thank you for your amazing explanation!
I somehow always thought that the “to the extent” explanation is easier to understand because it is “more visible” in English than just a little “so that”, but now I know better
I think I need to finally put this on my reading list 
Hey guys - I am little late to this book club (only just found these forums!), but am looking forward to Teasing Master Takagi-san . Just started to get into reading - i love these vocab sheets so much.
Wanted to mention that I’ve started a free community-sourced book grading site where you compare the difficulty of the books you’ve read and I then generate aggregate ratings. The whole interface is like a goodreads or bookmeter, so it also operates as a nice digital bookshelf too. I’ve gone through and catalogued most of the WK books, including this book which you can see i’ve already graded a little bit.
If you want to help out, you just have to create an account and mark a few books finished and i’ll prompt you to grade them in your dashboard. Any grading you do helps a ton. It’s still very much in beta (my personal project), so more descriptions / category tagging / public profiles is coming soon, but it’s already starting to be pretty cool i think! If you want more context - you can checkout the introduction on reddit.
I’m sorry this is a bit off topic, but thought you guys might be interested!
そのうちに、自分を直してくれた医者のように、「人の怪我や病気を直したい。」と、考えるようになったのです。
Before very long, he came to think, “I want to cure people’s injuries and illnesses”, like the doctor who cured him.
そのころ、日本はアメリカとの戦争の真っ只中にありました。
At that time, it was right at the height of Japan’s war with America.
治虫がそのとき住んでいた町にも、毎日のように爆弾が落とされました。
At that time the village where Osamu lived was also having bombs dropped on it almost every day.
戦争が終わったとき、治虫は十六歳でした。
When the war ended, Osamu was 16 years old.
Tomorrow’s a long one, and then the day after that is only one sentence lmao