I know how a jacket is supposed to fit. Also, it says it is a cotton/linen mix.
I think cotton/linen can be nice in the summer. It is more casual than wool, if that matters to you. At 5'7" 135# you are likely slim, but my only note would be that what is displayed on models and in ads, in my experience, is difficult to replicate in real life. I think GQ magazine is a great example, those models can't even tie their shoes in how tight the clothes are (for women, the same holds true with swimsuits, but I honestly am not one to complain). The earlier comments with regards to the BR jacket were, I believe, pertaining to how that jacket fit the model in that picture. I think it'd be easy to go up one, maybe two, sizes from that if I were to buy same. I think the need to accommodate for "real people" is what's behind J Crews "Crosby" line. The Ludlow line really didn't work for many in a real world setting, guys with like, shoulders and legs. ;-). Actually, my only reservation with either BR or J Crew is simply that I think they're a bit overpriced. Even on sale, I think there are better deals out there. My earlier endorsement of JCP is on the opinion that they provide a lot of value for the price, and their quality has steadily improved, faster than their brand recognition.
Lastly, I'm probably going to veer away from the usual Forum advise to buy for quality and longevity. You're young (I think) and an intern. You won't be that way forever, so buy what you want, make sure it fits. That's all. If you're lucky and have more resources later then buy better stuff.
