I can't really explain my fascination with these books. When I read The Girl with all the Gifts, I never imagined I would read the sequel — not because I didn't love it, but because I sometimes have the attention span of a gnat, and rarely follow up with series, trilogies, etc. because I just run out of steam. This is probably the same reason I have loyalty to only a few television shows and am quick to consider they've "jumped the shark". In any case, here I am again, reading a zombie book while my husband watches The Walking Dead (and no, I didn't give that show up, I was too chicken to even watch it.) Before I read The Boy on the Bridge, I watched the movie of The Girl with all the Gifts. Had I not been watching that on an airplane, I would have either cried in terror or shrieked like a little baby, because, despite knowing the entire plot and outcome, I was terrified.
The Boy on the Bridge is equally terrifying, at least to me, but in a completely satisfying way. If you have not read the first one, I am sure you can still read this as a stand-alone, but I recommend reading both no matter which order. The two stories are cleverly intertwined, so that the author considers it a sequel, prequel or equal, but that's merely semantics. Whatever he wants to call it, I'll read it. In fact, I will probably even read another. Bring on number 3.