Considering all the Let's Find Pokémon books you can see on that page, I don't think it's super-unlikely that this omnibus isn't manga-related.
There are 3 ways to go about (2 of which are conclusions to jump to)
1) The Conclusion that this is one of those "Let's Find Pokemon" books or a Information book (evidence: many other have popped up recently, cover looks similar to those of that stature) (evidence against: Diamond & Pearl won't be out in English for a long time and judging by the cover, this book appears to be in English)
2) The Conclusion that this is a manga book (specifcally a compilation of manga that never made it to volumes) (Evidence: Viz and Chuang Yi appear to be making similar moves in terms of Pokemon (reviving forgotten franchises, changing their manga from Left to Right to Right to Left format, etc.,.) since Viz made a commitment to compile a series into Tankouban (Pokemon Mystery Dungeon: Ginji's Rescue Team) it could be possible that chuang Yi has similar intentions in mind! Also, Omnibus means Compilation which may mean a compilation of short series and there are several species on the cover!)
Note: This is just a theory!