While I love floflo with all my heart and soul, I’m not sure anything on there will be easy enough for you, from what I can gather of your Japanese level. It’s designed to help people get into reading Japanese books, so the material isn’t really aimed at total beginners, unless your barrier truly is just vocabulary rather than grammar.
If you want to get an idea though, one of the easiest stories on there is ‘Obaa-san to Kuro Neko’, which is available for free:
https://floflo.moe/obaa-san-to-kuro-neko-aozora-bunko/
Maybe you could take a look at the text and, acknowledging that floflo will of course help tremendously with the vocabulary, see whether the grammar is in your range?
I’ve used Graded Readers and found them really effective for giving you reading practice and confidence. The ones I tackled have a Level 0, which I didn’t try, but the Level 1 texts were very simple.
The concept of reading without looking things up in a dictionary works well when the text isn’t too difficult for you to understand and the unknown words are at a low enough frequency. Graded Readers are also illustrated, which helps you to infer meaning even further.
http://www.ask-books.com/tadoku/en/
That said, they can be a little pricey (I’d recommend looking around to find the best prices). You get a CD with those ones which can also come in useful for listening and shadowing practise, but it’s something to bear in mind.
Otherwise, there are a few book clubs in the forums, and you might be able to find something at your level. This is probably the easiest text being tackled at the moment:
There’s also the Beginners Book Club, which is just about to start reading Aria. In general, manga can be a lot easier to tackle than books. Again, you’ve got pictures to help you infer meaning, but the sentences also tend to be much shorter and so on. Lots of slang can be something to watch out for.
Also, I’d bear in mind that the first chapter of anything is usually the hardest. You’re getting used to the author’s style, and there’s often lots of hard-to-read exposition. Try to persevere with anything you try out for a couple of chapters at least before making the decision.
Good luck with whatever you decide, and go for it!