Personally, I can't skim read - I've never been able to. I've always have to read word by word which can really affect my reading speed. This I've learnt over the years has had both positive and negatives as you might imagine.
In school it was a big negative, if something didn't hold my interest - bugger it - I wasn't going to waste my time and would get in trouble, but if it was interesting to me I'd spend the time and generally understand the content very well. In later life I've found myself to rely on article summaries to decide if I need to read the full source or not.
Reading a novel takes me a lot longer (say 2-4 weeks) than say my Grandfather who in his 90s smashes out 4-5 novels a week with great ease and while still leading a busy life, however he was saying to me that whenever he skim reads he knows he doesn't taken in as much information from the text and for him it's more about enjoyment of reading 'in the moment' rather than post-reading pondering of the book which I tend to do a lot more of.
Personally I find reading books on an e-ink screen a _lot_ quicker than an LCD screen like my iPad Pro and a still a little quicker than reading a physical book probably down to page turns and object weight.