"I found it slow ..."/"... too much detail"

It has nothing to do with the length of the book, or even necessarily the level of detail. It has to do with whether the quality of the writing keeps you engaged and moving eagerly through the book, or whether it flags and you have to make an effort to keep plodding wearily on.

Some detail is just not necessary. I had to give up reading the last Shardlake book because it was so full of completely unnecessary description - butchers coming out of shops with sheep carcasses, people emptying buckets, women at market stalls. It goes on and on and on.

His first books didn't need all that guff, we know Tudor life was pretty basic, and it completely diverts attention from the plot and destroyed any tension.

I can't even remember the book I was reading recently but it was soooo boringly descriptive I had to keep skipping it.
Descriptions about putting a pan of pasta on to boil, the water bubbles the steam.... oh just fuck off! kinda mind numbing stuff!

The Strike books are long not slow IMO. They are completely engrossing with lots of detail and it all feels relevant, the plot is always moving on. Whereas some long books just don't grip or engage me, the characters maybe don't seem realistic or whatever. Everyone likes different things.

It's personal taste. Some people like lots of plot, others are happy with not much happening and the focus is on the characterisation. Neither is right or wrong, just different.

This is not a criticism I've ever had of a book not written by Dickens or a Russian but it's as legitimate as any. Sometimes people just want something lightweight they don't have to give their full attention to, and that's fine with me.

Me, if I'm really engaged in a story, I want a richness of detail and for it to go on forever, but not everyone is me.

When I say something is slow, I mean that I'm struggling to get into it and for it to capture my attention. It's not about length per se - I'm very happy to read long books but only if they're not a slog.

Depends on context. For example, pretty much everything I read in first lockdown was stuff I had read scores of times before because there were enough nasty surprises going on outside my head without having them inside as well. Sometimes I want to read myself to sleep so I choose something light; and sometimes I want to be challenged or informed.

Because people are different.

Some people have too much going on in the day to day lives, and just want entertainment

Some people think that books where nothing happens are dull and boring