A convenient sized book, fits into a pocket or backpack neatly. A few car tours at the beginning should not put you off - the walks are well described and reasonably accurate. The local bus information is helpful if you are staying in or near Funchal - I wasn't, there was only one bus a day from our hotel, so I was somewhat restricted.
The book however, survived a soaking! On advice I layered toilet paper between the pages as it dried - used a whole roll, but the pages didn't stick! Like so many guide books, it's more use in retrospect; to enjoy the walks now I am home.