There is a difference between something being fun and challenging versus over the top and designed to kill players in the name of 'being hard'.
This module contains things like save or dies, unbalanced CRs, and hindering 'entries to combat'. There are mechanics that need to be prepared for, but no hint or indication of what is required before hand. So you're riding on blind luck that all your bases are covered.
If your character is not min/maxed or you happen to have a GM that enjoys killing players then AVOID THIS MODULE. I would have said I found it challenging but unfortunately it was eye rolling for most parts and then boring for the other parts.
Everyone will have a different experience with this module. Again, if you have a GM who enjoys killing players versus judging (like they're supposed to do), DO NOT PLAY THIS MODULE.