As interesting and relatively larger as Belgium and Holland are, Luxembourg has a ton of history - home base of the Roman Empire back in the 1100s...and northern Lux was the grounds of much of the Battle of the Bulge in Dec 1944 in WWII. They also are very appreciative of all tourism and Americans in particular as they see us as taking back their country for them from the German occupation.
There are so many wonderful spots - wine country in the south, Vianden in the east has the most gorgeous castle AND an adventure camp for families...You can get around everywhere in the country for 4 euros/day pass!
All in all, with everything else there is to see in Europe I don't know if I'd say this is an A-List destination, and perhaps wouldn't recommend this as a primary destination, more something to be combined with any of many easily-accessible cities by the fast trains (Paris, Brussels, Frankfurt, etc.)
But when a company is writing a tour book about it, they should give more than a few lines on each city other than Lux City. And the ratio of 181 pages (Belgium) / 229 pages (Holland) / to 39 pages (Luxembourg) was too skewed to help us much. Even in the largest section within Luxembourg pages, the monument information, etc. was sketchy and brief.
This is the first time I've been disappointed in a guidebook...but then again I more often use Fodor's...I wonder what their ratio is on pages devoted to each of these countries...Frommer's Belgium, Holland and Luxembourg (Frommer's Complete Guides)