The book doesn't specify what path to take for a good reason and that is the final goal is to master them a faster speed and exact path you take isn't as important as where you end up. A simple example is you may find that exercise 2 is easier for you then exercise 1 so you may be able to master exercise 2 at a bpm of 108 before you are able to master exercise 1 at 60 bpm. This most likely isn't the case, but you get the idea.

The Hanon exercises are very intensive and take a while to master. I suggest you only focus on one or two exercises at a time at a low bpm initially maybe even lower than 60 if you are having a lot of trouble. It will take a while to master each. [This site](http://www.hanon-online.com/the-virtuoso-pianist/part-i/exercise-n-1/) plays the execerizes for you and you can get an idea of how long it will take to play just the first excersize at 60 bpm not even considering you tying to lean it. When you master them and can play them faster you can string together a few exercises and use it as an excellent warm up for playing.