I do not have that book you mentioned, but I alreayd have too many books (I have a stack of GMAT related books about 1.5 feet high).
I already have an
error log incorporated into my studies; actually i have two - one I use to track my progress when practicing problem sets and one I use to track my errors on the practice CATs. The reason why I have the practice CATs sorted out separately is because my practice problems are usually untimed so the CAT log provides me with an extra dimension of data that includes a timed, endurance-requiring environment. Since my timing has been a huge problem the CAT log also lets me track how many questions I am forced to randomly guess on at the end of the test. This might not be for everyone is timing is not an issue.
I took a recent GMATPrep exam and boosted my score by 100 points (550 to 650) and I attribute that mainly to the fact that I was much more cognizant of timing due to my timed practice sections in my study plan.
I have also been revising my study plan like you have mentioned. I have put less focus on working practice problems and more focus on aligning review material with practice problems to match the review material. Here's my plan now:
1) Study concepts for "weakness of the week" - 30 mins
2) Sample problems for weakness - 40 minutes
3) Study concepts for "topic of the week" - 30 mins
4) Sampe problems for topic - 40 mins
5) Review ALL solutions for sample problems - 30 mins
5) Timed practice with old sample problems - 30 mins
The total time for that is more than 3 hours so I may decide to alternate weakness reviews with regular topic reviews every other day. That way I will continually be covering new material and working my weaknesses.