Cindy Meister
There just aren't any other (more) books available for VSTO than those listed.
If you need to learn about the Office object models, then you need material centered on the individual application. For Excel, I can recommend "Professional Excel Development" by Bullen, Bovey and Green (Addision Wesley). They even have a short bit in there on .NET and VSTO.
There isn't much out there for Word written in English, but a good (if somewhat out-dated) over-view of the OM can be found in "Writing Word Macros" by S. Roman (O'Reilly).
The best place to get a discussion going about books for any particular object model is a newsgroup for the particular application (see the "Please Read First" sticky message)