This is an interesting series.
It has humour so things don't get too heavy but at the same time they do loose people and there is violence and killing.

The series is a long one and these main characters stories continue for 3 seasons.
There is also a spin off series that deals with the sister later.

There is little intimacy. There is touching, hugging and a few kisses but no sex until much later in the last season.
The main 2 characters have love interests but due to the nature of the start of the virus and the constant threat there are no intimate scenes until the end of season 3.

Each season ends on a HFN with an enemy thread running through the whole series.
Each episode either ends as HFN with a goal set for the next or at times an immediate threat will run across several episodes.
At the time I read these the whole series was on Amazon KU so it was possible to read one after the other or complete in a box set.
If you start reading and want to get to a HEA you will need to read the entire 3 seasons.
There is the immediate zombie threat which is constant but also the series deals with humanities reaction to survival.
Often a bigger threat is the desire for power between the surviving groups and these at times use lack of resources and scientific experimentation to control the main threats.
Later in the series there is a love triangle situation of sorts for the heroine.
It's not exactly a love triangle but there is a dividing force between the main couple due to the interest from another man.
There are no intimate details but there is a kissing scene with the other man, but at the time the main couple are not together.
The characters are all very different, they have their flaws but they are college age so when they make mistakes and sometimes they are stupid ones I put it down to youth and although they have learnt survival through experience the threat is constant so it's not easy for them to be sensible all the time.
There is a good bit of banter between the group and a great deal of humour.
There are some serious issues dealt with too and the main human enemy threat is pretty evil. ( )