The guide book
‘Bhutan: a trekker’s guide’
(ISBN 978-1-85284-553-7)
is written by Bart Jordans.

This second edition was published in January 2008 in the UK by Cicerone Press, an outdoor specialised publisher with nearly 300 different guide books.

It is available directly through them, through several web book selling services or at any outdoor bookshop.