Its a great book with lots of exercises and useful tips. I don't know tho, I feel that I'm not doing much. I believe that language is something you either have or don't, so I think I'm in the safe side.
Do you have something to share with us? Books, sites…etc?
you can save $10 on the official practice test which issued by ETS and you can get the score instantly to see how is your TOEFL preparation. TOEFL practice online help you to feel more comfortable to the test and doing better in your real TOEFL! https://www.englishbaby.com/toeflpractice/choose_payment
And you also can get $50 on a online TOEFL course by University of Arizona as well.https://www.englishbaby.com/onlinetoeflcourse
There are past TOEFL test you can take and get graded by TOEFL. Maybe you can take one and see where you need improvement? TOEFL Online Practice Test >
Speaking is usually the hardest part. Here are some tips to prepare for TOEFL Speaking > In general, the more you speak English the faster you will improve and perform in your TOEFL score Test. Good Luck!