If you can get your hands on Lindsay Porter's book "MGB Guide to purchase and restoration" you will be in good shape. Tells you where to look for rust (not always apparent on these cars) , what to look out for mechanically, and how much problems will cost to fix.
Clausager's book is superb, but only useful in describing differences and originality, it doesn't tell you what you need to know when inspecting the cars. I have both books, well worth the investment.