Beyond Countless Doorways reminds of all the stuff of what make Planescape cool. In that, while we had the usual D&D tropes, they were given a completely new spin. Here though we are given completely new planes, each lovingly crafted to fit a particular view of what a plane might be. From a parallell world scenerio to even those that make the Far Realms seem almost inhabitable. Here your players can adventure, try to save a plane, or maybe help out the local powers. Along with stuff like Planar Wardens and even Planar Puroyver (both of which are some SERIOUS power increases for those that want to have potent forces.) Along with that alignements while not contraints, are still in play. Overall, Beyond is a greater source of Planar fun than even the recent Planar Handbook was.
I heartily recommend this awesome product for fans of both Planescape AND those wanting to see what real game designers can do with time, love and good effort.
(Oh also, Hyperconscious, not too shabby. You get to find out more about the Dark Plea, dreaming, future stuff, and some pretty cool crunch too. The extra stuff for Mindscapes is pretty sweet too.)