I took the Kaplan course
(intensive for 4 weeks - 5 hours every Sunday (2.5 hrs Math, 2.5 Verbal) in London and I found it very useful as it taught me a lot of strategies and shortcuts and familiarised myself with the test. However, once you have the content covered, the best thing is to practice with the real GMAT questions from the 11th Edition. Also the scores you get on the practice CATs in Kaplan
arenot necessarily an accurate reflection of what you will get on the real GMAT. Kaplan
tries to make the questions more difficult than the real GMAT but what that results in is questions that are not written in the same style of the real GMAT questions.
I took GMAT early Aug and got 580 so I am retaking on 12 Oct and am now using the Official Guide (OG) 11th Edition mainly and refer to the Kaplan
materials for the shortcuts.
Depends what your situation is - if you know the GMAT structure well then you don't necessarily need the Kaplan course
. Just use books. I went for the course to 'force' me to study the GMAT. Also depends how much time you have.
Hope this helps