The newest and best Hoya book is The Genus Hoya from Botanova Press. You have to buy right from the Botanova website and have the book shipped from Sweden. Hoya books are not numerous and for the most part they are fairly expensive. The older books have far too many misnamed plants to be useful and they can cause confusion by matching the wrong photos with the plant descriptions etc. I have quite a few Hoya books and The Genus Hoya is probably the best if you are looking for a general Hoya book. There are more scientific or in-depth Hoya publications but they are full of botanic terminology and are generally only for the very serious grower.

Now having said all that everything you will find in most books is available on the web for free. Sites like Hoyor.net and GrowingHoyas.com, or My Hoyas will give you all the info you will find in those expensive books. Often times the websites have more photos, photos of flower parts and pollinia etc. which you will not find in the books.

Check out Rainbow Gardens Books as well but generally the Kloppenburg books seem to be not worth the price. The Hoyas of Australia and The Hoyas of North Eastern New Guinea are much more scientific in scope and are not easy reading. There are botanical drawings in black ink and many botanical terms so they are not good for beginners. If you ever do want to dive into the world of botanical publications I would highly recommend Botanical Latin by William T Stearn as a fantastic book to help you learn botanical terminology and about the meanings of all those Latin and Greek names you see used in Botany.

Mike

Here is a link that might be useful: The Genus Hoya