"How We Learn" by Benedict Carey is the one I've read on the similar topic, and liked. It's a compendium of scientific research about learning aggregated in a readable format by NYTimes science journalist.

I second the recommendation for her course. It's a rare gem backed both by science and her considerable experience as an effective learner.

I don't remember "varying your study location" in that book.

She does mention it, something like "if you usually study in your bedroom, try recalling in the kitchen" or something like that

Ah, from this I was expecting it to be something with a little more expansion. I think I remember this.

I almost purchased that book. Is it working for you?

I am reading the book along with the course. "Mind for Numbers" is superset of the course, so see if you like the course and then maybe buy the book. So far I am pretty happy with the material and presentation. Armed with all this knowledge, the real challenge is ofcourse, to implement these techniques in your daily life, while breaking years of bad habits. But I am motivated enough to keep trying to do it.