The Bradt guide is highly recommended. It is current, well written and with excellent background/history/culture section. Detailed, appropriately opinionated and comprehensive reviews of hotels and restauranta. Good sections on Mafia island (to the south) and Pemba (north) - both of these are well worth choosing as the non-commercial alternative to Zanzibar main island. There is also a chapter on the southern mainland safari parks. In my view the dream holiday is Selous and/or Ruaha safari, then Mafia or Pemba for 4-7 days and three days in or near Stonetown on Zanzibar!