Gregor and the Marks of Secret
Suzanne Collins
It’s only a few months since Gregor and Boots returned from the Underland, leaving their mother behind to heal from the plague. Though Gregor’s family receives frequent updates on her condition, they all know Gregor must return to fulfill his role as the warrior who is key to the Underlanders’ survival.
Reviews

The story started to get more interesting at this point in the series because of all plotlines from the first three books started to come together. Gregor is still my favourite but I also liked Ares because of his interesting backstory. I would still recommend the series.
Inspector Viktor Hoverboard 04.09.2021

This was my favourite book from the series because it was written very well and it was hard to put down as there was a lot going on.
Anonymous 27.07.2020

Another one of the Gregor the Overlander series, can't wait to read the last book!
Anonymous 04.09.2017

Amazing. Hurry up and read this.
Anonymous 11.07.2014