The Door at the End of the World by Caroline Carlson

Lucy's boss has disappeared.  She was going to visit another gatekeeper and she never returned.  Lucy isn't supposed to leave her post nor is she to use the gate.  But she's afraid her gatekeeper is in trouble.  It gets even worse when a boy enters her world by accident.  He doesn't know how he got there.  And she needs to get him back home but the key got stuck in the lock and now the door won't open...

HarperCollins and Edelweiss let me read this book for review (thank you).  It will be published April 9th.

Lucy goes to find help but unfortunately she ends up held at headquarters.  By accident she finds out what the division head has planned.  And she has herself, the boy from another world, and a young girl smuggler to try to stop it from happening.

They run from world to world, almost get eaten by an animal that's worse than the Tasmanian devil, and the director and her henchmen want to kill them before they ruin her plans.

It's amazing that they live through all the things they do but they manage.  These worlds are magical and unusual (you can lose things without knowing it).  The doors are dangerous.  And nobody is on their side.  But they keep on trying.

I enjoyed this tale.  I couldn't wait to see what would happen next and there's plenty of action all the way through.  Middle graders should love this story.  I did.