The Site provides link to some useful books, which will help any aspirant pursuing Salesforce Certification. These books are extremely useful to build core skills for Salesforce Certification.
Salesforce.com Certified Developer DEV401 Practice Exams
by Mark Miller provides practice test which will be helpful for developer certification exam.
Force.com Developer Certification Handbook (DEV401)
by Siddhesh Kabe provides Sample questions for every topic in an exam pattern to help you prepare better for DEV401 certification. Anyone who is new in Salesforce can also go through this book and build expertise in salesforce.
Salesforce Certified Sales Consultant: Exam Preparation Study Guide & Workbook (SPCON-102)
by Steve Wasula helps to prepare for Salesforce Certified Sales Consultant Exam.This book covers all basic contents of salesforce like information about Standard objects, sharing rules, field level security, profiles, roles and many more topics of salesforce.