I've been using an Ee-ink tablet for almost two years since I've bought it.

You could also say ..."for almost two years." or ..."since I bought it almost two years ago."

It isn´t "I´ve" because that means "since I have bought it," which isn´t a phrase we would use here.

The first series of books that I've read on it was the "Three-bBody pProblem" by Liu Cixin Liu.

titles are usually written using italics, quotation marks, or underlining

I believe the name of the grammatical structure that uses "have" plus the past participle is the "present perfect tense," looking into when it is used may be helpful.

It grabbed my attention since I'd watched it on a summary about it on YouTube.

As it was written, "watched it" applied to "it" which meant the book, but since you didn´t watch the book, it needs revision.

Here the past perfect "I had watched" that you used works well, but you could also just say "since I watched."

you could also say ..."since I heard about it on a summary on..."

If any day I'm bored, I can pick a book and learn something and maybe start applying what I've read, inspired, by great guides.

This project is different from novels and non SciF-sci-fi books that I'm also reading.

genre names aren´t capitalized

Even though it looks weird, non- as a prefix tends to carry the dash with it when compound words are in play.

The first series of books that I've read was the Three-b Body pProblem by Cixin Liu.

It grabbed my attention since I'd watched it on a summary of it on YouTube.

I'll buy physical books about various topics on how to do x or y thing like medicine, mechanics, farming, and so on.

If any day I'm bored, I can pick a book and learn something, and maybe start applying what I've read, feeling inspired, by great guides.

I feel it would be more natural to say "If I'm every bored"

This project is different from the novels and non SciF-sci-fi books that I'm also reading.