Try a combination of some of these:
- RA Jishi - Feynman Diagram techniques in Condensed Matter Physics (standard 2nd quant., Green functions etc. found in older books, but very pedagogic. Not much on magnetism)
- Altland & SImons - Condensed Matter Field Theory (also has path integral methods - more modern.)
- C Nayak - Lecture notes on quantum condensed matter physics (Really good. These cover a wide range of topics)
- Lancaster, Blundell - QFT for the gifted amateur (tries to treat QFT without bias for HEP or CMP, but the authors are CMP and the way the subject is developed leans towards conventional condensed matter qft pedagogy. has a very nice selection of example applications of qft to many-body physics).
- P Coleman - Introduction to many-body physics (new book. I've only briefly glanced at some chapters. Looks good at first sight).
Some older good books are Mattuck, Fetter & Walecka, Ziman, Negele & Orland etc., but I personally prefer the books above (esp. 1-3).
Make sure you know your standard stat mech & intro solid state before you begin though:
For quick basic stat mech, David Tong's lecture notes are good. So is B.Cowan's "Topics in Stat. mech". Of course, master of all is Landau's Stat phys 1, but it will take a while to read. Other good books - Cardy's renormalisation & scaling, Goldenfeld's phase transitions, Yeomans's phase transitions.
For enough basic solid state - S.H.Simon (Oxford Solid State basics). If you're interested in more, Grosso & Parravicini's Solid State.
Particularly regarding the bose-hubbard model, I remember reading a very nice argument for it in a paper by Jaksch. Check his late 90s, early 2000s papers on PRL & Annals of Physics.