Feel free to post your suggestions on books about the period here. I'll start with two books dealing with the GNW:
-Peter Englund: Poltava (The English edition seems to be called "The Battle That Shook Europe: Poltava and the Birth of the Russian Empire"). This is a classic. Englund is a wonderful author with an engaging style, and the book deals with the battle and its aftermath in detail.
-THGC Publishing (ed.): Great Northern War Compendium. A massive two book set dealing with the whole war in detail. The books contain multiple articles written by different authors with varying subjects. All the participants are dealt with in at least some way. The books aren't cheap, but based on what I've read so far, I can heartily recommend buying the set!