I mostly play 2/5 live or 1/2 if its the weekends for the tourists or business men.
Harrington Books were my base when I started playing a decade ago.
If online I just play MTTs or stud variations
My favorite books for that are Winning Poker Tournaments One Hand at a time and Kill Everyone. For stud Seven-Card Stud for Advanced players by Sklansky.
Honestly now you can just look at tons of video content online, a lot of pros either have some free youtube videos of them multi tabling with their huds and going through their thought process during each session. Or replaying a tourny hand by hand. If you want to make an investment there are also sites with paid content where they update with 3-4 vids a week. I like videos more maybe because it adds the visual element to studying.
Hope they help, cheers