I joined Sun Microsystems back in 1997. My job, at least initially, was to support customers with their problems in case they were more complex than can be covered as part of a simple support call.
On my first day at the job, I got the usual introduction. Here's the computer, here's your account, etc. And here's a copy of "Sun Performance and Tuning" by @adrianco. Read it.
Well, I did. The next two days I red it from start to finish. It may seem like a weird thing to ask a new employee to do on the first day, but that book really got me through the next several years working for Sun.
Sun was really a special place at that time, and while I definitely have appreciated other places of employment, Sun was really somewhat unique. It was a place that were doing absolutely cutting edge stuff, while at the same time being open enough that I could contact pretty much anyone if I needed information.
I'm glad I had the opportunity to be part of that, and I'm sad that they didn't make it, and eventually were absorbed by Oracle, which probably (I had left long before that) didn't go any good for the morale of the people who were still there.