I find DI & LR tough while giving mocks due to limited time. Please suggest best or advance level book for the same.

There are plethora of books available but byfar the best have been mentioned below. 1.How to prepare for Quantitative Aptitude for the CAT by Arun Sharma. 2.Pearson Guide to Logical Reasoning for CAT by Nishit Sinha. Moreover, recommended to go through TIME Coaching Institute Material for solved examples and last 5year question sets for Quantitative aptitude. For Easy level problems, or for CMAT and CET preparation you should go with Chandresh Agarwal and notes from CETKing Coaching classes where there is elaborate pattern. All the Best

The strategy for solving DILR is selecting the right caselets and focusing on those in the given time limit. Also it's better if you practice DILR sets is sectional tests.

For your query regarding books, firstly you can get good practice questions in old cat papers and mock CAT by various coaching institutes. For books you can solve Arun Sharma's or Nishit Sinha's for DILR. Also you can practice from a good institutes practice material.

Solving these you should be able to crack one case in around ten minutes on an average.

I personally practiced LR DI from Arun Sharma, one of the most popular books/sources to practice LR DI.

You can start from the basic level of difficulty and then gradually move to the Advanced Level Of Difficulty. Both these topics LR and DI should be dealt with a different approach:

DI : Comparatively Easy but lengthy and tedious. Mostly, to solve these questions, the knowledge of basic mathematical operations is needed. To ace DI, you need to work on your speed. The faster you do it, the better it is.

LR: Tough and often time consuming. One needs to practice a variety of questions to gain confidence in this section. However there are certain topics like 'Arrangements' which are generally asked every year. So practice all varieties of such commonly asked topics.

To top it up, appear for mocks at regular intervals to track your progress and identify weaker areas.