Book of Kells

Hello friends,
I am looking for any advice about the book of Kells. We will be there the first week of September. I know we need to book in advance but where is the best to get tickets or get a tour ? What is the current info ? Many guide books differ and some online articles say parts are closed. Is the long room included in the entry price? Also, is Trinity College tour part of the experience or separate tickets. Thank you in advance. Val & Mark, Happy Travels