Every book is going to have bad reviews -- that's natural given the subjectivity of any given product.
I think Kaplan 2400's a little more approachable than Barron's 2400 and the practice questions, while difficult, more accurately represent the real thing.
Barron's 2400 and How to Prepare for the SAT are great -- but they're very dense (especially the latter). I wouldn't reccomend them to anyone scoring less than an 1800.
The key here is that you need to build your fundamentals -- 400s indicate a severe problem with your foundations. Your math score will be greatly improved with a refresher (or, in some cases, a learning) of the arithmetic, algebra, geometry, and other things of the SAT. After you know what you're doing, you can start learning how to solve the more difficult problems. But baby steps first.
For reading, you just need to get used to the questions and the types of passages. It's not your typical, hand-held story, but the SAT passages are either highly complex literary works or dense essays written by experts/intellectuals. Also, you could never go wrong by learning new words -- they help for both the sentence completions and reading comprehension (trust me -- it's a lot easier to understand what you're reading if you know what the words mean...)
For writing, I think you need to learn the grammar rules COLD. Your timing issue indicates that you had to think WAYY too much for each question. Learn all the grammar rules tested so when you see a sentence you say, "okay, this is error X, and choice Y fixes it the best without introducing errors Z, Q, or L". This section becomes instinctual after a while.
Also, look up any words in your daily life that you don't know -- it can only help. Plus, you'll be more interesting to talk to
