petera - your score puts you in the right range for this book. It also sounds like you may be having some stress management issues - it would be a good idea to address those as well. As you've learned, it's really hard to do well when you haven't gotten much sleep.
These two articles might have some ideas to help you:
http://www.manhattangmat.com/stress-tips.cfmhttp://www.manhattangmat.com/strategy-series-stress.cfmaritra - first, stop taking a test every day.
CAT exams are really good for (a) figuring out where you're scoring right now, (b) practicing stamina, and (c) analyzing your strengths and weaknesses. The actual act of just taking the exam is NOT so useful for
improving - it's a very inefficient way to learn. It's what you do with the test results / between tests that helps you to improve.
Your official test quant score is a little low for this book, but if you have been scoring 45+ on practice CATs taken under real conditions (normal timing, with the essays before, not a bunch of repeated questions / questions you've seen before, etc), then that's okay. Also, because you describe struggling with the timing, my guess is that your ability is higher than that 43 from your official test but the timing and solution process are messing you up - in which case, this is exactly the book that you want. It's all about developing good solution processes, learning more efficient ways to do problems, going back over your work to figure out how to avoid mistakes (which also mess up your timing sometimes, etc.
If you're taking the test in 4 weeks and you do want to use this book, get it right away. I think it takes at least 4 weeks to really internalize and be able to use the material given in the book.
I've just sent off an email to ask about electronic versions - I'll let you know.