I read it on my mission, actually I started it once on my mission, didn't finish it, then started over and finished it.
There are some things that Talmage does miss (Mostly Joseph Smith Translation) that changes some of the meanings of what is happening. But for the church to endorse the book (And publish it) its enough of the doctrine with what the church believes in.
The tough part is Talmage uses big words. On my mission I had this pocket dictionary that had most of the big words, so it does help to look them up instead of just guessing.
When I read it something about it just resonated with me and I couldn't put it down, I'm not a big reader I don't think I could honestly say I've read the book of Mormon all the way through, but I read Jesus the Christ in less than a week.
As tubaloth said it is published by the church and is one of the few books other than the scriptures that you can buy from the church distribution centers. Its also one of the only book again other than the scriptures that missionaries are allowed to read, why would they have the missionaries read it if it wasn't official church doctrine?
Jesus the Christ must be one of the best LDS books ever written. Elder Talmage is a wonderful and extremely intelligent author/teacher. I read the book 5 times on my mission, a lot more than I read the Book of Mormon. I highly recommend it, both to member and non-member!