I've not read Peopleware but I've read Why Does Software Cost So Much? by Tom DeMarco and Slack by Tom DeMarco. The former focuses on technical issues and the sunken cost of software. The latter focuses on the agility of organisations. Tom DeMarco started as a programmer and subsequently became a consultant increasingly focusing less on technical issues and more on business issues. Therefore, reading his books in order would be most relevant as your start-up develops.