TOS: Crucible: McCoy - The Provenance of Shadows (My All-Time-Favourite)
Vanguard: Reap the Whirlwind (Makes no sense without the first two of the series)
TNG: A Time for War, A Time for Peace (The entire A Time to - series is recommendable)
DS9: Terok Nor: Day of the Vipers (Could also be considered Lost Era)
Voyager: Full Circle (You can skip the first VOY-Relaunch-books, this one sums them up sufficiently)
ENT: What Price Honor (Since you asked for one out of each series, this one at least made it to upper middle-class, in honest, ignore ENT, none of the novels ever excited me... )
Titan: Orion's Hounds
New Frontier: Stone and Anvil (Entire NF-series is good, just start at the beginning and work your all through it)
Corps of Engineers: Wildfire (Not sure if it makes any sense to read this one, if you're not familiar with the series, if you are, it's damm good)
The Lost Era: The Art of the Impossible (The first two in the series, the Sundered and Serpents among the Ruins are also highly recommendable)
Klingon Empire: Honor Bound (Continuation of Book 1, A Good Day to Die, makes no sense to read just one and both are good)
Others: Articles of the Federation
Stargazer: Haven't read any of it so far
Mini-series: Destiny
Vanguard: Reap the Whirlwind (Makes no sense without the first two of the series)
TNG: A Time for War, A Time for Peace (The entire A Time to - series is recommendable)
DS9: Terok Nor: Day of the Vipers (Could also be considered Lost Era)
Voyager: Full Circle (You can skip the first VOY-Relaunch-books, this one sums them up sufficiently)
ENT: What Price Honor (Since you asked for one out of each series, this one at least made it to upper middle-class, in honest, ignore ENT, none of the novels ever excited me... )
Titan: Orion's Hounds
New Frontier: Stone and Anvil (Entire NF-series is good, just start at the beginning and work your all through it)
Corps of Engineers: Wildfire (Not sure if it makes any sense to read this one, if you're not familiar with the series, if you are, it's damm good)
The Lost Era: The Art of the Impossible (The first two in the series, the Sundered and Serpents among the Ruins are also highly recommendable)
Klingon Empire: Honor Bound (Continuation of Book 1, A Good Day to Die, makes no sense to read just one and both are good)
Others: Articles of the Federation
Stargazer: Haven't read any of it so far
Mini-series: Destiny