WBH is a great book. The design systems for objects fit together really well, so you end up with a real-feeling star system. You get enough information about the objects to give a quick description to the players if they go there. If they need to know if there's a certain chemical in the atmosphere, or what the surface temperature is, for example, you can find it out. The outputs are much better than the T5 alternative.
Of course, by hand it takes so long to do the math that I'd consider it practically unusable on its own. Fortunately, there's the autogenerate program Stargen, and you can generate a complete star system with a click. You need the WBH to interpret the results.