Books should be chosen based on our comfort zone. You read the book for sometime and if u feel its comfortable, u buy one for yourself.
Try TN Manoharan book for DT , Vineeth Sodhani for IDT. V S datey is good for IDT.
Dont choose V.S.Datey. Its huge n its given from practic purpose. Without 2nd thought u can choose BANGAR for self stdy. And how much u marks it depends hw much u understand the conceps, provisions etc. , not on selection of authors. Ofcourse, 1st of all book shud be gud, presented in a understandable manner and along with dis ur effort also required to get exemption. Bangar buk+icai case law buk + pm. .more than enough. U can rock.