CBI conducts its recruitment exam In month of FEBRUARY.
You will find its notification in EMPLOYMENT NEWS in month of NOVEMBER.
Its SELECTION PROCESS consists of ...
Written Examination carrying: 400 marks
General Intelligence and Reasoning
Personality Test (Interview): 100 marks.
i. English Language
ii. Language Comprehension
iii. Communication / Writing
iv. Ability Test
For preparation...refer to books like...
RS AGARWAL QUANTITATIVE APTITUDE
RS AGARWAL VERBAL AND NON VERBAL.
Best of luck..