The illustrations here are so-so and nothing more but the story is pretty cool. It's obvious this wasn't published in the past few years, it has a dated sort of feel to it IMO, more dated than it actually is really. I think the title probably gives the story it's description right there. A little boy is walking upstairs to go to bed and he's full of "what if's" on the way. Lots of cool "what if's" that'll make any kid with an active imagination plan to implement these exact scenarios, maybe even with a few twists on them of their own. Julia's about 5 1/2 and she enjoyed it very much but I also think it could be read to younger kids also - maybe older toddlers and up.
Mr 6 got this from school library. I really liked it- fun imaginative story. Mr 6 found it a bit dull and only gave it a 6/10. So might be better for the 4/5 yos