Originally when the Harley Quinn series began, I despised it. I thought it was a terrible depiction of the character and the artwork gave her the appearance of Marvel Comics' She-Hulk in a harlequin costume. I even went to the extreme of starting a petition to submit to DC Comics for Ty Templeton to write the series. I never got a response back so obviously, they thought the idea was ridiculous. Those were back in the days when the series was written by Karl Kesel and the drawings were done by Terry Dodson. I really don't know which of the two were worse.
In November of 2002, the series went through an overhaul with a new creative team. One that dramatically impacted the series, giving it somewhat cartoony artwork while remaining in the mainstream style. One with dark humor that somewhat matched Harley's witty tongue from the Animated Series. One that made her somewhat seem like the Harley Quinn we all know and love. The storyline was actually interesting and worth reading, whereas before, it seemed as if they threw a random story together just to make the fresh, new character in the mainstream continuity have her own series. The current writer of the series is A.J. Lieberman and Mike Huddleston took the job for pencils.
As with any series, though, there have been a few faults. One minor one is that they spell Harley's real name "Harlene" in Lieberman's first issue, though, he might have done his research and this might be corrected in further issues. Harley's origin is somewhat jumbled in issue 26. It refers more to the origins of "Mad Love" rather than Paul Dini's one-shot that introduced Harley into the mainstream. It's basically Lieberman's own spin on Harley's origin, which I guess is exciting in it's own way, though I wish he would have followed along with the one-shot. Also, Arkham Asylum looks more like a high security jail than a home for the insane. Can't have everything, I guess.
Below is a complete collection of the covers of the series, starting with issue one.