You can't force anyone to read the books you found helpful. I don't really know if you'd want to, isn't diversity even better?
However, I think there are some ways you could subtly steer your slaves team to be more what you want them to be.
1: Barriers to entry
The first thing to do is to remove all 'barriers to entry'. I.e. don't make them buy these expensive books from their salary. For example: make sure there is a fund for each developers with which they can buy their learning material. failing that, a 'library' of sorts could provide books which they can borrow to read at home, new books could then be requested by your developers and acquired by the company for all to use. I do not think you should let them read books under worktime, unless directly related to what they are doing. Good developers have at least one programming book at a time on their nightstand (Right next to the Hitchikers Guide of course).
2: Use a carrot
The second part of the plan is to add a little motivator. Be clear that you want your team to grow as developers and make it an important part of their periodic assessment. They'll get a better evaluation if they have shown growth, and will get a bad evaluation if they do not. A salary increase should be coupled with this assessment which is only logical, a growing developer increases his value to the company. (And again, because it in the end is about making money, make sure they know about this!)
3: Get better people
The third part is hiring the right people. Every new person in your team should be one that is willing to learn, obviously! This has two advantages, not only do you have someone that is willing to learn but someone that will lead through example. Not learners will hopefully see that this new whippersnapper (and every old member that does take up a book or two) is climbing the ladder relatively quickly in respect and eventually in salary, which should motivate those still resisting.
4: Remove the bad people
The fourth and final part of the master plan is to remove the bad apples. Developers that do not want to learn even after all barriers have been removed, subtle pressure has been applied and saw what could come from applying yourself, should not have a place in your company. The negative assessments they will have accrued by now will help you to build a case to fire them. Although firing someone is not a happy occasion (well...there are those instances... ;-) ), you will have removed a bad influence and as a bonus you now have a place to hire one of those whippersnappers.