I tried to read the first Thomas Covenent in my early twenties - thought it was awful got about half way through it and gave up. I thought it was a fifth rate Tolkien imitation.

There must be other books I regret having started but they seem to have been wiped from my memory.

Dicken is definitely a struggle (I've just restarted Bleak House after a gap of about 3 or 4 years: the new BBC version is just brilliant btw) but it's worth putting in the effort to get through the pages of dense descripition that lesser writers would get through in half a sentence!