I used to get stressed about it when dd was a year old, and try to keep her on my lap and get through the book as quickly as possible, then dh told me he just let her wander around while he read the story. So I took that approach too and after a while she would sit to look at the book. Definitely by 22 months she loved books and enjoyed having picture books read e.g. the hungry caterpillar and would talk about them and point things out.
Ds1 was even worse for sitting still, and at 18 months we were definitely still on board books with 4 or 5 pages and touchy feely bits. Now at almost 4 he loves books. He still fidgets a bit though and tends to like 'reading' his own book (very loudly!) while I am reading a book (that he has chosen) to him!
Now Ds2 will rarely sit through more than 5 pages, even of his favourite books, but I just finish the book without him and get on with the rest of bedtime! IN a few months I know he will be able to concentrate for longer. HTH