Junk Force is a manga that probably would've done really well as a short tv series or OVA. Since it's only a three volume series that runs 18 chapters, it's short, cute, yet a very bare-bones manga that could've worked into a pretty decent plot if it were longer, given some of the teasers at the end of the later volumes.
[STORY 5] A world destroyed by something leaves civilization a wasteland. The heroes are (surprise!) a group of 12-16 year olds gathering scrap monsters and or parts to salvage as cash. If you've played the Atlus game Metal Saga, it's not at all different from that. It's pretty straight forward and nothing surprising, every other chapter is either semi-linear or just a subplot to insert a few ecchi jokes here and there. It's mostly played for comedy, and that's all right, but this could've been a post-apocalyptic style Slayers or something.
[ART 8] Junk Force's artwork, while the character designs seem a bit uninspired, is pretty good. If not for the character's themselves, then the atmosphere. There is some pretty good detail in the junk-laden cities and metropolis areas. The tank units and motorcyles all look really sleek, it just screams to be animated. Battles are crisp, and the action scenes never get too crowded or cluttered.
Character designs, as stated before, are very good, but do little to stand out from the cliches they are limited to. Fan service is one of the driving points of this title, but it's pretty harmless stuff. Some curvy teens in bathing suits, a hot spring or two. Even a ridiculous chapter where the air conditioning breaks down, so you know what that means!? It's such a lame excuse to get girls into less clothing that I actually found it funny. What I enjoyed about the fan service in Junk Force is it's retro approach to use it as comedy; none of that modern-styled "fall into girl and pull off her towel" crap that runs rampant today. It's simple and funny and that about it.
[CHARACTER 5] The characters are a typical group of ragtag teens. Liza is the straight leader of the group, Louis is the token male who gets abused by his female superiors and hinted love interest of Liza. Wooty is the big-breasted loud-mouth and muscle of the team. Mille is the brainiac whose a horrible cook, and Mamet is tacked on cuteness whose also an invincible android. That's pretty much all you need to know and that all they tell you.
[ENJOYMENT 7] The chapters make for a brief, fun read. I really enjoyed the chapters about Mamet and she became my favorite character. Watching the girl abttle it out over whose the hottest one of the three is entertaining. The short length means you could read this all in one day if you wanted while at the same time it's not bad enough to warrant the worth of dropping a 3 volume manga.
[OVERALL 6] Junk Force has little upside, but it's an enjoyable adventure while it lasts. It's got the feel of an hour long OVA. Some nice action scenes and decent comedy keeps it from being marred in mediocrity, but it's better than I thought it was for an 18 chapter story.

PROS: Nice artwork, decent old-school comedy
CONS: Not long enough, no character development