As of my experience, one can crack SCJP with the help of few books and materials.
Kathy sierra and khalid mughal are the two best books to crack SUN certification.
If you want to have in-depth concepts, go for Head First books.
I strongly recommend those books to acquire complete knowledge and to get maximum score.

I suggest the dumps also but without preparing these books, dumps alone can't do anything.

I had the links to those books try them.

SCJP 6 By Kathy Sierra

SCJP 5 By Kathy Sierra

SCJP By Khalid Mughal

SCWCD 5 By David BridgeWater

SCJP Practice Tests By Kathy Sierra