I too have a high opinion of MGMAT. While that volume is not as impressive as their other material, it will be hard to find anything else in print form that will surpass it. IR is such a new question, that there hasn't been much time to gather data and form informed opinions of it.
I will recommend this free IR eBook. http://magoosh.com/gmat/2012/gmat-integ ... ing-ebook/
I hope you find it helpful.
Also, in case you find it helpful, here is a review of GMAC's official website with 50 IR practice questions. http://magoosh.com/gmat/2012/gmacs-offi ... -new-gmat/
Best of luck to you. Let me know if you have any further questions.
Magoosh Test Prep