There's the official EU Books timeline here http://suvudu.com/files/2012/03/SW_T...March_2012.pdf
I started collecting when the prequels came out; I have now several periods entirely. Like the Old Republic Era, the Rise of the Empire Era, the Legacy Era, and new books published in the other eras. It really depends on what you're into, the kinds of stories you like to read. And then there's audiobooks. They're quite good, with Star Wars sound effects and soundtrack and so, it's very emerging. It got me to get the New Jedi Order Era in Audiobook format. The New Jedi Order is not one I'd start with, it's not a bad period per se, but it's less Star Wars and more sci-fi. The Yuzhang Vong and the stories there get into some pop sci-fi ground that to me wasn't that appealing. I like the Star Wars books that have political intrigue and adventure.
The Darth Bane books were mentioned, they're not bad, and written by Drew who was lead writer for SWTOR. I feel these books mostly deal with canon continuity. It explains the rule of two, that'd been referred to before in other books and comes down to what has been said in the prequels; there can be only two, one with the power and one to crave it. A rule that had been ascribed to Darth Bane, and the trilogy delves into the life of Bane and his apprentice. It connects the Old Republic, an era with thousands of Sith and Jedi, to the later periods with thousands of Jedi and two Sith. It makes a good read, it can be classified in the personal story category. Revan would be in the same category, it tells you about the life of Revan after KOTOR and before SWTOR. There are a bunch of books like these that can be read singularly, they're not part of a series. They're good books, but they make shorter stories compared to the books that are part of a series.
The series of books tell one story, written by a group of writers, with way more characters over a longer period of time. Lots of different events, culminating to an end of series event. These books are really what hooked me on SW Literature. There's lots of things happening in the galaxy, on different planets by different factions, and it's told from all kinds of viewpoints.
The Clone Wars literature, that unfortunately has been moved down in the canon tree (due to the children's cartoon network series popularity), was the first literature I got. It's a line of stand alone books that share the clone wars background. There's stories from Yoda, Mace Windu, Obi-Wan, Anakin, Count Dooku, etc. They're adventures on a single planet, you'll read about the political background on that planet, how the Jedi come in as diplomats/keepers of the peace, to resolve issues that threaten to plunge the planet and the sector in the galaxy into war and possibly the arms of the separatists. There's stories about the people on that planet, their species, their force background etc. Planets are really varied, there's urban planets, and tropical forest planets, rural backgrounds, tribal planets, etc. It shows how diverse the Star Wars galaxy is more than any other era. It places these stories in a larger situation that you know, the prequel movies, mostly EPI and EPII.
The Legacy Era literature is different. It continues the stories of the heroes. Han and Leia are married, had three children, and Luke and Mara married and had one child. It will continue their stories in a larger galaxy, they are on more planets, but you find out less about the galaxy and more about the story of the larger galaxy; what happens to the new Republic and the Imperial Remnant and its heroes. Unlike the Rise of the Empire Era, these books make one story, over several novels. That adds in many ways more depth to the story. It makes richer characters that are more developed, and more characters overall. And not to add many spoilers, but there's really a lot of interesting things happening, children falling to the dark side and a galaxy plunged in war yet again. It's told from the perspective of mostly force users, unlike the other era where troopers and other players also have their perspective told.
The Legacy of the Force series deals with what happens to the galaxy when someone falls to the dark side again. It's probably my favourite series. It has perspectives of the new Darth and the Jedi told. There's also history on the Mandalorians, their language, their culture etc. Boba Fett comes into play. It can be read without knowing much of the previous series (I hadn't read any of that when I started it). Though you might want to pick up the Dark Nest Trilogy at some point, as some of that comes back and also later again in the The Fate of the Jedi series. The rest of the New Jedi Order is not really necessary to read, all you need to know about it will be (re)told in this series, and the elaboration on that is not really relevant to the series.
The Fate of the Jedi series deals with an unknown force being, and finding a planet full of Sith (which links to the Old Republic era; Pandemonium). Jedi go mad, they don't know why, and public opinion is not with them, one of them fell to the dark side in the previous series after all and now there are mad Jedi going around. But it's also a lot about Luke's legacy, and at times I found reading about his teenage son and the teenage issues a bit annoying. But there's some romeo and julliet there, forbidden love. Oooh. And we learn of what might have created the galaxy. And for the first time really, we learn about some Sith culture. I would recommend reading Pandemonium from the Old Republic Era at some point while reading this series, as they are related (when this series was released they put a chapter of the book on the net for free a month before a new book was released).
I also enjoyed Knight Errant a lot. It's a single book (for now, I asked the author about the possibility of a series, and he said it was out of his hands but he'd like to write it). It's set in a new period in the Old Republic Era and is quite rich in describing the Sith Galaxy. In this period there's a great divide in the SW galaxy, part of it is Republic and part of it is Sith. Both know very little about each other's parts of the galaxy. And here one Jedi Knight gets lost in the Sith region and discouvers much of Sith culture. It's an era where there's several lineages of Sith, they all have their own way of ruling, and have divided their part of the galaxy. They're at war with each other, and with the Jedi. I liked reading it, as it's got lots of characters, planets and so on. But it leaves one wanting more, and for now there's none coming.