Hi Franch! My DD1 was 20mo when DD2 arrived so quite similar. There is a book called New Baby in the toodler talk range by Ladybird. It is written by Marie Birkinshaw and costs £3.99. I found it really useful, it has all different scenarios on each page ranging from preparing for baby to feed times and bath times etc. The only thing my DD didn't like was that it was about a boy and his baby brother! The book is for upto a 3 year old. Hope this helps. I found all other books were for older children.
I think - I've just looked, but it seems to be buried under other books - that ours is New Baby too. DD1 firmly thinks the small boy is her. Even though he looks nothing like her. But that I suspect says more about DD1 than anything else
are both really good picture books, my DD loves them, there are pictures int he waiting for baby which show going for the scan and getting the nursery ready and the new baby one has pictures of a mummy breast feeding
We had the Ladybird book for DD (20m age gap) and she still makes me read it 4m later! Because the mum, dad and toddler all have short brown hair like us it was easy to use her name when reading it so she related to it really well.