I usually tend to rate 'first' maps a bit high, but in this case the five stars would have been earned even by a very experienced mapper!
This is absolutely magnificent. Excellent brushwork, fabulous mood-setting, filled with crooks and nannies.... er, nooks and crannies...
Good lighting, good monster placement (perhaps with the shambler and vore right after the gold key as an exception).
If i should compare this to anything, i guess ad_sepulcher would come closest.
I certainly hope this mapper will continue to produce new maps; but be warned! My expectations for You will be very high!
Thanks for Your excellent work, and thanks for sharing!