I have not yet started reading books, but I tried https://satorireader.com, which seems like a good starting point for reading practice.
EDIT: Maybe I should extend my post a little… just posting the link might be worthless.
As @Dadung already said, knowing Japanese grammar is important. I had a similar experience as him when visiting NHK easy and could barely read a thing.
I liked that in Satori Reader, every word is clickable and then shows the translation (but I guess there are web-browser extensions that allow you to do the same on every Japanese webpage). Sometimes they also added helpful grammatical explanations. You can listen to every sentence, and there is an integrated SRS for vocabulary that you encountered during reading. It is possible to link it to your WaniKani API key, so that vocabulary for which you didn’t learn the Kanji yet is only shown in Hiragana (or Kanji with Furigana).
The downside is, that only some of the articles are free - for full access you need a subscription.
So if you have no problem with reading digital material, I would recommend Satori Reader or alternatively NHK easy, maybe in combination with a browser extension to look up vocabulary.
If you prefer reading physical books, but want to look up unknown vocabulary on the PC, you could try Houhou, which is a dictionary that also contains an SRS tool.
I’m new to learning Japanese and don’t know many resources yet, but maybe this was helpful for you (or somebody else).