I'll give 4 stars on everything simply because you're an original author, and your book has potential, however, Mark's arrogant internal monologue just ended up giving me a headache, his character that didn't fit the descriptions you gave at the start made him even more annoying to the point where I had to give up at the end of the rooftop chapter, and just skim read ahead to at least give a reasonable review... the main things that led to my problems with Mark are that quite simply, nothing about him makes sense, he's unusually handsome yet apparently is massively depressed, self confidence is extremely important in making someone seem attractive...
the man was seriously considering suicide, I get him wanting to live because the zombie apocalypse is fascinating, but if that's the case, he'd either entirely forget his desire to die, or spend some time coming to terms with it, not mention it every few minutes for you to seemingly, bolster your word count, which is honestly what the first chapters felt like...
then, there's his arrogance that seems to shine through when speaking to the woman that saved his life because he stupidly said he wanted to fight some zombies, then decided to run around a sofa instead, while still acting like he's freaking action man, and seemingly, no-one even blinked an eye to it...
the hints at him being a gamer in the first chapter seemed really important, then his actions didn't even slightly follow that trend, a gamer would come to terms with there being zombies fast, sure, but there are other important things they'd remember too, like if there's a corpse twitching on the ground, stab it in the head, they wouldn't just loot first, and let the zombie turn in the same room as them...