Where to start with room acoustics

Here's the simple answers/problems/issues to deal with:

Easier to get good sound set up along the "long wall" for the inexperienced, and with less acoustical treatments. You want to start with seats, and try 1/3 or 1/5 possitions. IF you sit closer to your speakers with a "short wall"(sitting down the long wall facing the short wall) setup, you'll also have acoustical advantages in hearing more direct sound vs. reflected. Othewise, ACOUSTICAL TREATMENTS ARE MORE OF A MUST!(Compared to a long wall set up).
You want to get all your speakers set up in relation to your seats where you get FLAT FREQUENCY RESPONSE in the bass!(20hz-300hz reigion)...or as close as possible, making sure of response in critical crossover points. Also, exact phase between speakers and sub(s) is a must for coherence and balance. You can either move around the room and listen for best spots(then measure) while you play music through one speaker(summed stereo) that's placed where your head will be(or vise versa) for best bass response!(easy), or simply use test tones/discs and sound meter and measure for best response for EACH SPEAKER and sub!
In short, balance is Key! Once you get good seating possitions(I recomment maybe 2 to 4 at most in that narrow room(see old issues of SGTHT mag's "Home theater architect" for "set up/seating instructions"), you want to make sure the balance of soundstage and imaging is good...proper width/perspective in relation to screen for proximity, proper "toe-in" for tonality, "aiming" for soundstage perspective, etc. You will strongly be advised to do acoustical absorbtion or diffusion at the first reflection points on the walls/ceiling between your ears and the speakers if you do a "short wall set up", and better also for "long wall setup"...also, absorbtion behind your mains speakers(dirrectly behind mostly/only).
Your overall room balance is more absorbtion up front vs. more diffusion/reflection in the back half of the room. Things can get more involved with "reverb" and others, but consider more on the reflecton side to gard agains "over damping" and a dead sounding room. Still, with sread out absorbers around the front half especially, you should be ok, otherwise diffusors on the sides with some abosorbtion. If speakers are out more in the room, not so much concern up front with absorb/diffuse, so maybe a little behind speakers with either. (see HT mag's March issue(?) for their "echo chamber" article for custom HT)
Don't sit near walls, and more out in the room (again, consider odd multiple seating ratio's like 1/3's, 1/5's, 1/7's, etc. In relation, you want to look for even number multiple placements as starting points for speakers(1/6's,1/10's,etc).
This is all pretty accurate for a "closed in" room. OTher considerations for rooms with odd shapes/dimmensions and openings to other rooms/spaces. Still, you want flat/even response for all speakers and sub(s) from the listenging possition, (to hear more dirrect sound) to treat reflections which color and couple with the dirrect sound, proper soundstage width, tonality from toe-in, as well as "aim of speakers" for proper soundstage/height/perspective/etc.
Can you change dimmensions by moving walls? How about ading floating floor? If everyting is set there, a low pile carpet is good for you likely.
Basically, that's it! Otherwise, consult. for maxium results. But, doign what I said correctly will get you an easy 200% better results than most end up with ever!...and light years towards a top notch experience.
Most people don't realize how much all these variable add up, or WORK AGAINST YOU if you don't adress them! Small rooms like these are work!..but well worth it in your goal to make the acoustical enviroment and visual experience duplicate the experience as it was intended...special!...massive!..dynamic!...balanced!...uncolored...detailed...and accurate! Good luck...and don't forget proper bass mangagment...AMEN.

MY experience suggest that you enlist a projessional! You simply won't, that's right won't ever get the best of what you could be getting if you don't get the room right! The room, set up, calibration, tweeking, acoustics, etc, all add up to more than half the sonic equation! If you spend a bit of money having your acoustics all sorted out, considering seating possitions, speaker placements, calibration, acoustical treatments(often not that much, from companies like PMI,etc, which are superb and effective for little!), you'll be WAAAAAAAAAAAAAAAAY AHEAD of where 99.99% of all people mostl ever end up, even with the most expensive gear money can buy! Infact, peoples acoustical spaces are often so poorly adressed and heavily challenged(13x27x8 is a small space acoustically, and needs help and proper considerations adressed indeed), that they haven't a prayer when it comes to getting truely world class sonic playback!
If you consulted many of the acoustical experts out there(again, people like Rives audio anda the people at PMI can be of tremendous and afordable help with simply aiding his help and affordable acoutical treatments, which I had the pleasure to audition at the Show last year).
There's unfortunately no substitute for professional help! These people have spent their lives learnign and perfecting this stuff! The gear is only part of the equation, remember that.
Another "cheep" alternative that can help is to READ READ READ! There are many many acoustical writings in Stereophiles guide to Home Theater mag, HT magazine, AV Interiors mag, etc out there, as well as books like you mentioned. Still, unless you have experience yourself, you will only go so far. Depends on what you want out of it.
To be true however, having sold Hi-end gear for 15 years, at the low to the ultra high end, my experience is that most never get the acoustics issues handled properly, and thus their systems often end up being mediocre to poor overall. That's the way it is.