Just wanted to know is the level of actual gmat similar to og questions and gmat prep or tougher than that ?

Flash card is the convenient way to prepare for the GMAT. Hope you enjoy it.

GMAT Flashcard Secrets: GMAT Exam Practice Questions & Review for the Graduate Management Admissions Test

Borders GMAT Flashcards

Barron’s GMAT Flash Cards

TOP 5 Essential GMAT Books
The best 5 GMAT books compiled after voting from GMAT aspirant.

The Official Guide for GMAT Review
The Official Guide for GMAT Review, 12th Edition

Kaplan GMAT 2010-2011 Premier with CD-ROM
Kaplan GMAT 2010-2011 Premier with CD-ROM (Kaplan GMAT Premier Program (w/CD))

Cracking the GMAT, 2010 Edition (Graduate School Test Preparation)
Cracking the GMAT, 2010 Edition (Graduate School Test Preparation)

The Official Guide for GMAT Verbal Review
The Official Guide for GMAT Verbal Review, 2nd Edition

The Official Guide for GMAT Quantitative Review
The Official Guide for GMAT Quantitative Review, 2nd Edition