What are interesting books needed a vocabulary of about 4,000 words?
RondSorheim

I could recommend Paolo Coelho's books. They have relatively easy language and not to long sentences and also really interesting stories that are hard to put down and perfect for beginners. I've used several of his books as my first read book in different languages; in Spanish many years ago I read the Alchemist and gained a lot even though it was kind of a drudge occasionally; also it being my first foreign language apart from english I didn't know what I was doing, but it worked in the end, I think thanks to the simple language of the book. In Slovak I read his book Veronika decides to die as my first book, also Coelho's simple language and skyrocketed my comprehension in a short amount of time.
ericb100

Here's maybe a possibility:
No idea how exciting the story is. It does say intermediate to advanced (progressing)...so might be a touch to high? Was going to suggest Olly Richards books, but doesn't look like he has any for Greek.
Diary of Wimpy Kid in Greek might be a possibility. I've found traces that there might be those translated to Greek, but may only be in physical copy.
Hopefully others who've studied Greek can chime in on some good choices.
Also clarify, that you are, indeed, looking for choices in Greek. If a different language you may have a lot more possibilties.
Cinderela

How can I upload books bought on Amazon to lingQ?
azarya

download Calibre and remove the DRM with the DeDRM plugin
Cinderela

Thanks. Does it always work? Does it put the file at risk? Can I download the file in PDF format?
azarya

it always works if you install it correctly yes.
The file itself is not at risk.
You can convert it to quite a lot of different formats using the tool, including word, epub, mobi, and pdf I think.
bbbblinq

Thanks. I may go back to paper at some point. It's a good level.
ColinJohnstonov

I am currently reading translations of the Goosebumps books by R. L. Stein. These are easier and shorter. Also Nancy Drew books are doable.
azarya

At that point I would either read really simple stuff, look at what is recommended for first years of elementary school or opt for news articles and such.
Else, If really fixated on good books, I would take the plunge and read something far above your level. Whatever keeps you motivated to go on at that point.
JulianiTOgo

I actually don't think that Harry Potter is that easy.
For many languages you will find graded readers. Those are books especially written for language learners. They have a more limited vocabulary and use easier sentences.
When it comes to translations you could give The Wizard of Oz and The Little Prince a try. I'm not sure if the language is easier than in Harry Potter but the small chapters are a huge help. The Wizard of Oz is also really repetitive and with a clear, straight forward storytelling.
ColinJohnstonov

I've been trying Garry Potter in Russian and it is really difficult. It is about the same difficulty as the translation of A Brief History Of Time which I also tried reading. Le Petite Prince is much easier.
ericb100

I found it really difficult when I started it. I think I started around 10,000 LingQ words. By the end of it I was far more proficient with understanding it (by then I probably was up around 15,000).
Another series at a similar level is the Percy Jackson series. It may actually be a bit easier, but since I read it at 20,000 LingQ words or so, it *was* easier from that aspect. There were still some tricky points, but it actually felt like a very nice comfortable level.
I see your Greek is the one around 4,000 words...I'm wondering whether your choices may be a bit limited. I think Juliani's suggestion for graded readers is a good one. I'm pretty sure Harry Potter is available in Greek even if it is very difficult for your level. Not sure about Percy Jackson series.
I like Colin's suggestion of Nancy Drew or maybe Hardy Boys? Not really sure their level, but I read them when I was young.
bbbblinq

Thanks all. With a little more research, some option I would like are not available. I could move to the Secret Garden or Matilda, but my interest would be lower. Harry Potter is mentioned just above the Gruffalo in one list of books (for natives speakers though).
I think I'll persevere with Harry Potter. I'm very happy reading it and I'm beginning to expect to understand it rather than rely heavily on the translation.