There are lots of threads like this in the
science book discussion forum. I usually tell people to get Griffiths and Isham first (and read both at the same time), and then Ballentine, but maybe I should replace Griffiths with something else. Several people have said that it's not that good. I assumed that it was because it got positive comments from several people here and when I used the "search inside" feature at Amazon, I really liked what I saw. Maybe the rest of the book isn't as good as the parts I read.
In one of these threads, someone suggested the book by Nouredine Zettilli. It looks like a very interesting option. It has 13 reviews at Amazon. The only two who gave it 4 stars instead of 5 said that they did it because it had some typos.
Isham is a must-have in my opinion. The full name is "Lectures on quantum theory: mathematical and structural foundations". It's cheap, short, easy to read, and focuses on the mathematical formalism (without getting into the heavy stuff). It's more about what the theory actually says, than about how to apply it.
I also recommend that you get a good book on linear algebra. ("Linear algebra done right" by Sheldon Axler looks very good to me, but I have only read a few pages in it). Some of the QM stuff is impossible to understand without a solid understanding of vector spaces, linear independence, inner products, orthormality, eigenvectors and the relationship between linear operators and matrices.