It's a mixed bag. Often more on the nose than a pair of nostrils with its religious musings and with typically undisciplined Flanagan-esque meandering monologues.
However, it does work far more than it doesn't. I think some of the religious aspects amount to zen level trolling! There's some very convincing acting and character development, and also effective classic monster moments.
Overall I give Flanagan's Lot 4 out of 5. It'd be interesting to see if there could be a heavy edit for a film version - that might have been more to my taste.