Jessica Jones is an agent with the Metropolitan Special Branch.
Being such makes her one of the police officers who span the gap between the normal Scotland Yard detectives whose normal clientele are crooks and murderers and rapists and other low-lifes, and the operatives from MI-5 and MI-6 who make seem to have more glamorous assignments but who lack the ability to legally apprehend their own forms of miscreants.
Jones, being with Special Branch and having been there for some time as the series starts, gets a wide assortment of cases which tasks her abilities as both a cop and an eventual supervisor but these same assignments and the way she handles them also reveals how very good she is at her job. By no means perfect and with the tendency to take her job a bit more seriously than might be good for her mental well-being, Jones is impressive to those who work for her or over her and even to those who have the misfortune of running up against her. The latter, though, tend to show their appreciation for her skills by shooting at her, a less than desired form of accolade.
As the series opens, she is 35 years old, divorced from a marriage many years before, living with her boyfriend and fellow SB officer, Tom, and quite happy with her life. She has worked over her career in the various sub-departments that the Special Branch handles so she knows her way around an investigation, interviewing witnesses, and, for the kind of work she is getting into now, being able to handle herself in a battle. While she has not had to yet take a life, that fact changes very early in the first book, an action that really brings out the seriousness of her job.
By description, she is on the short side, being around 5'3 and fairly light but judging by the number of times men meeting her give her frame not once but often two looks indicates she is quite pleasant to watch. She does not flaunt her sexuality but she does not hide from it either. Like most things in Jones' life, it is so she deals with it. Jones is not light-headed or silly or ditsy. She is not callous or jaded or cynical or angry. She is a normal person doing an unnormal job and she is quite good at it, getting better as each adventure passes.