not sure what you mean by good. The standard books on quadratic forms over number fields are in Hanke's references. I would add that Hanke studied under Shimura, so you should take a look at [shimura_2010][1] and [shimura_2012][2], as the standard interplay is quadratic forms and modular forms. Note that the book that defined notation for a generation is O'Meara, in Hanke's references. I'm not sure Hanke mentions [Kitaoka][3]. 

For other classical groups, [Grove][4] is unusual in including characteristic 2 in full detail.

Finally, i never got interested in using number fields. So i like [Cassels, Rational Quadratic Forms.][5] 

 


  [1]: http://www.springer.com/mathematics/algebra/book/978-1-4419-1731-7
  [2]: http://www.springer.com/mathematics/computational+science+&+engineering/book/978-1-4614-2124-5
  [3]: http://www.cambridge.org/us/academic/subjects/mathematics/number-theory/arithmetic-quadratic-forms?format=PB
  [4]: http://www.ams.org/bookstore-getitem/item=GSM-39
  [5]: http://store.doverpublications.com/0486466701.html