For me Lonely Planet books do exactly what they say on the tin, and for the kind of holidays I like going on, I'll pretty much always make sure that I'm taking the relevant Lonely Planet with me.
This Finland book is no exception, and helped us find some great places to stay and to eat, many of which we wouldn't have otherwise found out about. We pretty much always agreed with the brief comments in each review as well.
There's a worthwhile 50 pages introducing Finnish history and culture at the beginning and the rest of the book is sensibly organised, starting with Helsinki and the South and working up to Lapland towards the back of the book.
I know this sounds more like an advert than a review but we couldn't fault this book on our recent Finnish trip, and it was well-thumbed.