The Monstrumologist is a great series, you can't go wrong with that one. A few other YA recommendations off the top of my head:
The Maze Runner By James Dashner - dystopian science fiction trilogy.
Airborn By Kenneth Oppel - Jules Verne style adventure in a steampunkish setting.
I Am Not A Serial Killer By Dan Wells - A really good urban fantasy trilogy.
The Returners By Gemma Malley - Fantastic book that shows YA isn't just for kids
Time Riders By Alex Scarrow - A fun time travel series.
Have fun, there are some really good YA novels out there that can be enjoyed by adults as well as children.