[emadabdulrahim]

You can use both strategies depending on the book.

If you're unsure about the book, then strategy number 2 is better. Skim and find the interesting bits, if any.

If you know it's a dense book and you value the subject and think highly of the author. Then strategy number 1 is better.

[philipswood]

Yes, agreed.

Personally I tend to go with a just-read-whatever-is-interesting-at-whatever-speed-or-level-of-attention-feels-right-and-what-sticks-sticks strategy.