Karen Traviss is an author who wrote the Star Wars: Republic Commando series as well as Halo: Glasslands. She is well able to flesh out the Gears of War universe using what I assume are extensive background notes from the game's creators at Epic. Each book has a number of flashbacks which all overlap each other. Four out of five books have been released and I decided to read them all in chronological order, not in intended page number; but not even Gearspedia had a helpful timeline for me to work with. So, for anyone who wants to know in what order to read the books and play the games, below is what I have mapped out.
The four books are Aspho Fields, Jacinto's Remnant, Anvil Gate and Coalition's End. A fifth book, The Slab, is due out in May 2012, as of this posting. There are two different date systems used in the sagas based on the Pendulum Wars and Emergence Day. As far as I can tell no approximate Earth date has been given, so it's up to you to decide whether this is a future Earth colony or an alien planet with humanoids. I favor the former. [note: in Aspho Fields there is an error in date for a number of chapters as being set 16 years before E-Day. It should really be 2 years before E-Day. I account for that below.]
80 years before Emergence Day a new fuel source, Imulsion, was discovered deep underground. This led to the Pendulum Wars almost immediately and eventually involved all the nations of Sera, split between two sides; the COG and UIR nations. Eventually the UIR surrendered six weeks before Emergence Day. Prior to E-Day dates were counted as years after the Pendulum War started, so the siege of Anvil Gate took place during the 62nd year of the War. After E-Day and the near extinction of the "human" race on Sera, they referred to dates as Before Emergence (BE) or After Emergence (AE), which places the siege of Anvil Gate at 17 BE. The Seran day has 26 hours and the calendar includes months named Bloom, Frost and Rise. It can also be assumed that a Seran week is a least 7 days long.
62nd year of the War (17 BE)
Anvil Gate: chapters 5, 8, 11, 13, 17, and 19
67th year of the War (12 BE)
Aspho Fields: chapter 3, part 1
70th year of the War (9 BE)
Aspho Fields: chapter 3, part 2
75th year of the War (4 BE)
Aspho Fields: chapter 5
76th year of the War (3 BE)
Aspho Fields: chapters 6-7
77th year of the War (2 BE)
Aspho Fields: chapter 9-10, 12-13, 15-17, and 19
EMERGENCE DAY
Coalition's End: chapters 4, 7 and 11
1 AE
Jacinto's Remnant: chapters 3 and 6
Coalition's End: chapter 14 part 1
Jacinto's Remant: chapter 9
Coalition's End: chapter 14 part 2
Jacinto's Remant: chapter 13 parts 1-2
Coalition's End: chapter 14 part 3 - page 250 line 32
Jacinto's Remant: chapter 13 part 3 - page 290 line 19
Coalition's End: page 250 line 33 - page 251 line 12
Jacinto's Remant: page 290 line 20 - page 292 line 13
Coalition's End: page 251 line 13 - line 22
Jacinto's Remant: page 292 line 14 - bottom of page 292
Coalition's End: page 251 line 23 - page 252 line 8
Jacinto's Remant: page 293 (end of chapter 13)
Coalition's End: page 252 line 9 - end of chapter 14
Jacinto's Remnant: chapter 15 part 1
Coalition's End: chapter 17 part 1
Jacinto's Remnant: chapter 15 parts 2-3
Coalition's End: chapter 17 parts 2-3
9 AE
Coalition's End: chapter 20
10 AE
RAAM'S SHADOW
The Slab: chapter 1
The Slab: chapter 2
The Slab: chapter 3
The Slab: chapter 4
The Slab: chapter 5
The Slab: prologue
The Slab: chapter 6
The Slab: chapter 7
The Slab: chapter 8
12 AE
The Slab: chapter 9
The Slab: chapter 10
The Slab: chapter 11
13 AE
The Slab: chapter 12
The Slab: chapter 13
The Slab: chapter 14
The Slab: chapter 15
14 AEThe Slab: chapter 15
The Slab: chapter 16
The Slab: chapter 17
The Slab: chapter 18 - page 484 line 15
GEARS OF WAR: ACT I / The Slab: chapter 18 pgs 484 line 16- 494
The Slab: epilogue
GEARS OF WAR: ACT II - V
Aspho Field: prologue, chapters 1-2, 4, 8, 11, 14, 18, 20 and epilogue
GEARS OF WAR 2
Jacinto's Remnant: prologue, chapters 1-2, 4-5, 7-8, 10-12, 14, and 16-18
Anvil Gates: prologue
15 AE
Anvil Gates: chapters 1-4, 6-7, 9-10, 12, 14-16, 18, and 20
Coalition's End: prologue, chapters 1-3, 5-6, 8-10, 12-13, 15-16, 18-19, and 21-23
16 AE
GEARS OF WAR 3
[UPDATE Jan 25, 2012] Now that I'm reading more of the events surrounding the use of the Hammer of Dawn during 1 AE I have to improve the chronology. Some of the events overlap so I tried to separate them in the best places, but you can take it with a grain of salt.
[UPDATE Jan 26, 2012] Raam's Shadow doesn't have much timeline info in it, other than to say sometime after Emergence Day. After doing some online research it appears (from Gearspedia) that the events of the downloadable scenario are about a decade after E-Day. It tells the tale of the Kryll-Storm attack on Ilima, which is a precursor to the Battle of Ephyra (set in 10 AE according to Epic's timeline). I am not including the "lost chapter" from Gears of War 2 simply because it is an alternative explanation of the events following the death of Maria, and I prefer the actual game.
[UPDATE Jan 31, 2014] The Slab is the only book in the series that doesn't rely on flashbacks. No need to jump around the narrative as in the other four books. This is the story of the Marcus Fenix's betrayal during a key battle and his four years of prison time, leading up to the first game. The story starts in 10 AE, and as Jace has a small part in the books, it takes place soon after the game expansion Raam's Shadow. Special note should be made that the last half of the last chapter is a retelling of the very first mission in Gears of War, Act I titled "14 Years After E-Day". It covers the game from Dom finding Marcus to the Grub attack in Embry Square after meeting Hoffman in the cut-scene.
