What do you think president Trump’s favorite book to read is?

I thought he was illiterate 

Since he is illiterate, he probably has to get books on tape and I don’t know if they offer Mein Kampf!

The only confirmed book Trump's come near to in the past years is Facebook.

It's been purported that Trump has never read an entire book in his life. (I think, this is something one of his ex-wives once said but I might remember wrong.)
Now, that might be an exaggeration but, frankly, nothing coming from him makes me think that he's a reader.

They reportedly dumbed down the Presidential Daily Brief to one page with pictures and he still doesn't read it.
Here's an article which would be concerning in any other presidency but hardly registers in this one: https://www.businessinsider.com/trump-looks-at-charts-in-intelligence-briefings-2020-5
The article contains the following quote of Trump's from an earlier Axios interview: "I like bullets or I like as little as possible. I don't need, you know, 200-page reports on something that can be handled on a page. That I can tell you."
This statement doesn't necessarily mean that he's never read an entire book in his life but it certainly doesn't give you the impression that Trump is a reader, either.

A colouring book probably or if that’s too complicated , a sticker book.

Assuming Trump reads books they are no more difficult than "
Dick and Jane, Baby Sally and Spot" or "Green Eggs and Ham"

He does not have the time.
He is busy running the country, and guiding his people.

He has claimed the Bible is his favourite book, yet in an interview in 2016 when he was asked to tell the interviewer of a Bible verse which meant something to him, he was unable to name a single one.

Trump's 2017 remarks at the National Prayer Breakfast compared to Obama's the year before also makes me question whether this book or indeed religion mean anything to him.

Probably his own autobiography! 

Main Kampf, the cat in the hat, who knows. God bless trump.

Probably about politics. But he could be interested in fiction or cooking or other genres too, depending on his interest. You can research more about what he is interested in.