[ToJans]

IME you do not need to read everything thoroughly to get value out of it.

I usually go through several spurs in a year where I go through a series of books in a couple of days... I might not recall everything that's being said, but I get the main message, and assume a lot of information is stored subconsciously.

Simply knowing that there's more details available if/when I need it is usually enough for me...

The technique to learn to speed-read is easy, but it takes a lot of practice. I posted a reply explaining it; no idea why it got downvoted TBH.

Anyway, I'd strongly suggest you to start practicing; it tends to be a very valuable skill to have.