Toddler Ask to read book/Read Book interaction cancels

Me too, and not just Read to Toddler interaction. Train to Potty or Read to Sleep are also glitched. I have to click on the toddler and have them ask for those things so that the adult sim does it. It also helps if I first use the Pick Up interaction, and then choose one of those. But choosing directly with the adult sim to do these interactions paralyzes them and then it cancels the action.

Me too. When the toddler approaches a visiting sim - Agnes Crumplebottom is a great bff for this, btw - they can ask the visitor to read to them and the interaction works correctly. I'm only having trouble with it failing when the toddler asks their mother to read to them, but the mother needs to spend two hours reading to a kid so this is a serious problem.

happened to me today

I've had this issue since I started playing Sims 4 about a year ago.  If the adult and toddler Sim are already sitting together on a couch or loveseat when you attempt the interaction, they perform it without issue most of the time.  If the Sims are not already seated together when you select the interaction, it times out before they can both get settled and the interaction cancels itself.  Sometimes they will move towards seating, sometimes they'll just stand there.  

The same problem. Mac, no mods. Very annoying and another toddler related issue.

.. Also, by going about it the other way and having the parent offer to read a book to the child, I get an instant pop-up asking if their family dynamic is "strict." No, she's not "strict", she's offering to do what the toddler just asked her three times to do, and I'd prefer her not to be accused of basically being a controlling mess just because she's reading to her kid like they asked her to, thanks.

Maybe you could create new topic for this? It doesn't seem right and it looks like another thing that went wrong :/

Same here and it's weird because it only happens with the father (who has Big Happy Family Aspiration) and not the mother.
Fyi, I disabled all the packs to play with the base game, life and death, island living, backyard stuff and basement treasure. 

I have this issue too. 

It only works for me when I have both parent and toddler sitting on the couch together. Have the toddler ask for a book or the parent ask to read. The toddler agrees, gets off the couch, crawls back onto the couch, then the parent successfully reads.

Any other time they ask for a book, the parent pulls out the book and both parent and toddler stand around doing nothing for a couple of seconds then the action cancels. It's like they want to try to find a nearby seat but can't so it just times out.

I have the issue with infants, too. I can only read to them if I put them in a crib then have the parent sit in a nearby chair or toddler bed.