I had the same situation. I got a verbal offer, that was then sent as an e-mail offer with details from the department head. The next step was the formal written offer, which came in the form of a letter. This letter was scanned and e-mailed to me, as well as sent via postal mail. When it arrived via postal mail, it came with an employee background form and a form authorizing them to use my SSN to put me on payroll. When I saw that, I felt pretty confident that this job was really going to happen. :) But, I never got an additional, more formal contract beyond the letter. The letter referred to itself as a contract, but there was none of the heavy legalese that I was expecting—simply an explanation of the terms of my salary, length of contract, and references to the faculty manual, which contains a lot of the expected legal stuff. Purportedly, the contract is binding once your signature is on it, so once you do that, I think you're safe to cancel the other interviews. At least, that's what I did! Congrats on the job!