Treat comprehension totally seperately from decoding words.
Start by looking at the book title and pictures - what do you think the story will be about and why?
After the first couple of pages - who have we met? what are they like? what do you think might happen next?
Keep going and stopping at suitable intervals, after exciting bits or when something looks like it might be about to happen - what do you thinkwill happen? how has it made the character feel? how do we know this?
And similar at the end too.
Obviously how much you do it depends ont he child and the mood they are in. After the first attenpt it doesbecme less obvious, a bit more subtle, and not make you feel like you are constantly interrupting them.
But comprehension is really important and worth maing the effort over.
OK, this very long thread has some quite interesting discussion on comprehension interwoven amongst the bits of various people rehearsing their prejudices (and me sounding embarrassingly pompous, I've realised, reading it back. So apologies and skip that bit).
In a sense, comprehension depends on their passive vocabulary. Mine always get really annoyed if they ask them about stuff, particularly DS2. DS2 often zones out during our bedtime story and I realise he hasn't understood the last page or so, but I guess that's a time for relaxation and him enjoying the sound of my voice.