I think there is an issue if you expect people to understand Latin to read it - relatively few do these days, but some will. This means that not only do you have to provide explanations/translations, but these have to be accurate!
I have read some stories where Latin phrases/mottos etc are used, with an expectation that the read will know them - sometimes this is fine if they are well known, but it does provide a barrier to reading. Umberto Eco, IIRC, tends to do this, but then he draws from such a wide range of back-tales, all of which you really need to know, this is just part of my problem.
Using Latin for the names of things or people is not a barrier really - you can recognise the names whatever the actual language is, whether Latin, Vulcan or an Elven language. Using it as the lingua franca of a book raises a whole lot of other issues, not least about language development.