I read “Cinderella” from the “Disney Golden Collection” in Japanese. I managed to go to a Japanese book sale when I was in uni (years ago and I hadn’t studied Japanese seriously since) and nabbed a copy. It’s one of those hardback books - for children obvi. All hiragana…about 20 pages with like a sentence each lol.
Many vocabulary words were unknown to me ofc. Lots were from WK levels that I haven’t reached. However, I understood many more words this time after studying on WK than when I bought the book. Words whose phonetic sounds were familiar to me by way of learning kanji gave me general ideas of the meaning.
Examples:
ばしゃ（馬車）the sound for horse and car, “carriage”
ぶとうかい （舞踏会）knowing that “kai” usu means get-togethers.
But I think being familiar with the story itself and the story having pictures helped.
Grammar structures that I hadn’t yet covered but managed to find on Bunpro: (I’m on N4 chapter 2 for reference)
(N3, chapter 11, lesson 1)
Verb[よう]＋とする - Show state which you are about to do an action
(N4, chapter 14, lesson 2)
subject 1~とsubject 2 - simplest way I understood it was “when” in the context of the sentence
(N4, chapter 18, lesson 4)
ことになります - used when a decision has been made by someone else
(N3, chapter 13, lesson 1)
[verb plain]ようにと - used to warn someone of something or give an order
Also the passive voice of verbs.
They were used to uncover the meaning of sentences like this:
そこで だいじんが くにじゅうの
むすめに ガラスの くつを
はかせて みることに なりました。
Given that it’s all hiragana, I think the spaces helped… the spaces don’t really show up when I type on here.
Honestly, my reading comprehension was much better than I expected. For pages that made my eyes roll into the back of my head and made me want to put the book down, I skipped and came back at the end. Turns out they were less intimidating than I thought. I just had to be patient. Was able to get through the book mostly(?) understanding everything.
But again, I think being familiar with the content helped. 
With that boost to my confidence, I think I’ll try a chapter of よつばと！ for the next few days.