Just wanted to update this thread regarding Borneo field guides.
A second edition of the Susan Myers guide came out in 2016, and I would recommend it as the go to identification guide for Borneo. (Note that Amazon and some others erroneously list its publication date as 2012 for reasons unknown.) Unfortunately it is a tad pricey as I write this.
I do not recommend the Phillips' guide (third edition, 2014) as a primary guide. It lacks any identification information for many species, and in many other cases the identification information is sparse or inadequate. (It expects you to ID many birds just by looking at the plates--a proven method of unreliable identification). However, it should be a good supplement since it makes for more interesting reading overall, and has a good deal of natural history and other information that is lacking from the Myers' guide, which tends to be rather dry.
Also, the Birds of the Indonesian Archipelago guide mentioned in the preceding post covers all the birds of Borneo. It is too heavy and includes too many species not found in Borneo to recommend as a primary guide, but it does have taxonomic (and possibly ID) information not found in the other guides.