I bought a bunch of them a few weeks ago. They are very good and very friendly reading, a good intro to the faith for non-Catholics and a good reminder for Catholics. Good for you, we need more Catholics willing to go out and do this sort of thing. Imagine if all Catholics did it.
I also bought a bunch of Pillar of Fire booklets, which are even better but they are larger and cost a little bit more.
If you are going to leave them at a parish make sure you inform them and get permission. (As anyone in a Church should be wary of someone dropping stuff off like tracts, and need to make sure they are appropriate.) I had a priest who was kinda gun-shy about it, probably for good reason as we live in an area where people are always trying to evangelize Catholics.
These things are great though for Churches to have on the way out of Mass also.
