In my opinion, shoes are the hardest/bulkiest thing to carry (unless you have to bring a computer). I know you mentioned that you can't leave stuff at work, but if you can find a space to stash just those, I think it would make your commute that much easier. Aside from that, if your commute is short enough & depending on your work dress code, you can just wear your work shoes on the bike (there are plenty of shoes that are athletic enough for the ride in, but also dressy enough for dress casual).

Again, depending on your commute distance, I find that I can wear my work pants (Dockers) if the temperature is less than 55-60. If it's hotter than this, I wear shorts & pack the pants.

If it were me, I'd skip the rain pants & get a very lightweight rain jacket. I have a GoLite Echo jacket from a few years ago. It's not waterproof, but is good enough to get me home dry unless it's raining hard (7 mile commute home).

I'd mount the pump to the bike & put the tools in a small bag under the seat (unless you park in a place where people will steal the tools). Also, you can probably get away with just a multi-tool, patch kit, pump & extra tube (maybe a wrench if you don't have quick release wheels.)

If you can bring a kindle or ipod/iphone type device to replace the books, that should drop the weight dramatically. Kindles are small, but ipods/iphones (and droids, etc) are multi-purpose, so if you're carrying a phone already, this is even more weight to shave.) I wouldn't want to make an iphone my main reading device, but it works great for me for work & with the kindle app or ibooks, you can sync amongst devices, so if I get to page 100 on my iphone at work, when I start to read on my ipad at home, it syncs to page 100.)

Bike water bottle cage for the water bottle.

I commute with a backpack strapped to a rear rack (using Surly junk straps). I roll up my work clothes into the backpack, along with a light jacket (GoLite Echo or Nike pullover, depending on the weather) & put my wallet & iphone in the top pocket.
I leave my tools on the bike, but if I felt unsafe doing so, I'd put those in the top pocket on the backpack along with the iphone & wallet. If I carried a lunch, I'd put that in the pack as well. Put a water bottle on the bike. then when I get to work, I can throw the bottle in the bag (Camelbak Podium bottle-when locked closed, it never leaks) & carry everything with me over my shoulder. I've seen lots of bags that have a helmet carrier on the outside so you could even put that in the bag as well. I'd be surprised if my current setup weighs more than 5 pounds. Adding lunch, a helmet & a pair of shoes would increase the weight somewhat, but overall, I'd still never call it heavy.