I've traveled around my back yard in Houston, Galveston, and Corpus with both this book and the Moon Texas Handbook. Lonely Planet is pretty much on the mark with what attractions they've included and which they haven't (as well as with the ones they've dissed). From reading Moon, you'd never know that Moody Gardens in Galveston is a total rip; You'd also think that it would be worth the time and the shelling out of $3 to visit the Institute of Oriental Cultures in Corpus, the home of a few exhibits randomly strewn together with very, very minimal interpretation.
As far as restaurants go, it appears to me that the listings in Lonely Planet concentrate on rather hip places with cheap prices, regardless of the quality of the food, while Moon tends to imitate the listings in the Houston Chronicle and Houston Press. I guess which you would prefer depends on whether you're a 'foodie' or if you just want a cheap place to nosh.
One deficiency of this book is the lack of coverage of outdoor activities. Moon definately surpasses Lonely Planet in this regard. If you enjoy both outdoor and urban activities, you might need both guides.
The only thing that irritated me about this guide (I almost couldn't get past it)was its constant bashing of Houston and the climate. Several 'insights' the writers had to the area were based on faulty assumptions, but, I guess, at least they had an opinion. Furthermore, Houston's climate is a tad bit milder than nearby New Orleans, and they didn't bash that city for its climate. But that's a minor complaint compared to how useful I found the guide. (And the maps are also excellent --- showing the location of most of the text.)