I have been a fan of TOS and TNG since i was a kid and TNG was on the air. I have now discovered the extent of the novel series and plan to start reading much of the older ones, probably in order of publication starting with the motion picture. Without going back and watching the tv series, will i miss out on a lot? Or are major tv storylines covered in the novels. Eventually i will get into the other series such as DS9 and Voyager, but have lots of time prior to that.
You should watch DS9 before starting the relaunch novels - firstly because you need the back story, and partly because DS9 is easily the best Trek series !
A few novels are direct sequels to TV episodes. Usually in those instances, the "historian's note" suggests the episode you should see first. A great many TOS and TNG books are fairly standalone, requiring only basic knowledge of the characters and setting to be enjoyed. As Relayer1 says, don't attempt the post-series stuff unless you've seen the series' they're based on since they're direct continuations. Although it may be interesting to try some of the earlier, standalone DS9, Voyager and Enterprise novels prior to seeing the shows - just to compare the mental image of the characters you get from the books to the on-screen versions.
However in the case of DS9 and Voyager, even reading very early novels will spoil the events of the first episodes.
Not really. I'm currently going through the numbered Voyager novels, and while they do talk a lot about the pilot and how Voyager ended up in the Delta Quadrant, the books barely touch on any other episode. But for Enterprise, I would suggest that you read the novels prior to seeing the TV series. I was first introduced to Enterprise with the books and I found that when I saw the episodes, the episodes paled in comparison to the books. Enterprise should've been left for the books.