Chosen isn’t so much a book as it is a program. It comes with a set of videos, an instructor’s guide and student workbooks. Not every video is great but many of them are. Remember, confirmation programs are not set on personal opinion, but rather do they meet the needs of the students, the diocese, and the Catholic Church as a whole.
There are several youth ministry resource sites. Christopher Wesley is doing great work, Marathon Youth Ministry, Dr Bob McCarty has great info on communicating with youth.
I get a lot of activity ideas from Pintrest, I just modify them to suit or needs. With all youth the last thing they want is to sit in another classroom and be talked at. They get enough of that at school. Youth ministry, including confirmation prep, needs to be experiential. It needs to be at their level, not that the information needs to be dumbed down because that is not true at all, it just needs to meet the kids where they are, how does this apply to their lives today? Youth ministry needs to be interactive, if you and your co-teacher do all the talking the kids will learn very little. They will put in the time, do just enough to make it to confirmation, and then just leave.
I can’t stress enough that cobbling a program together from various sources is NOT a good way to go. Supplementing an approved program with some other resources may work but it takes a lot of experience to know what will and won’t work. You’ll get many opinions of what should and shouldn’t be included, especially from folks who don’t work in youth ministry, but the bottom line is to prepare the youth for a life in Christ with confirmation.