I just finished Harry Harrison's Deathworld trilogy. It's widely available in combined or separate editions (the link above is for the first book in the series. I read from an old out of print omnibus edition, though there are omnibus editions currently in print).
As far as a quick, easy, fast paced action scf-fi thriller, this series delivered. The plot of the first book is the most exciting - it deals with survivors fighting off a planet where it seems everything (and I mean everything, right down to the blades of grass and the minerals in the rocks) in inherently deadly to humans. A galactic adventurer plops down in the middle of this survival tale and notices that almost none of this makes any sense, since 90% of the time these deadly features have no evolutionary advantage. And then there's those humans who farm the countryside and aren't getting attacked by the flora and fauna every waking hour....
Each volume moves at a quick pace, never giving you time to think to deeply about what is (or might be) going on. Characterization is at a minimum, but it's a fun read. At least the first book is. The second book is mildly offensive, since Harrison decides that to provide comic relief he needed to ridicule religion. But that's a minor nit. The real problem with volumes two and three is that after dealing with a planet where everything wants to kill you and there is no chance for rest or relaxation, adventures on a slave planet and amidst a hunter-gatherer society just seem anti-climactic.
Also, the last volume paradoxically endorses both capitalism and totalitarianism, since the hero uses terror and mass murder to unite all the tribes under one powerful leader. In the end, he manages to get them to embrace capitalism, and thus a relative peace, but *never mind* all those people you helped kill along the way.