One question that I often hear is, “Do we have to implement Scrum by the book, or should we adapt it to our environment?”

The answer is, “Yes!” You should do both. And, they are not mutually exclusive.

To me, 'keeping Scrum pure' means adopting the three roles, four meetings, four artifacts, and two levels of commitment, and adhering to the principles behind Scrum, e.g., self-directed teams that commit, timeboxing, etc. This aligns with the Construx toolbox metaphor for software engineering best practices; Scrum is the tool rather than specific Scrum practices or processes.

'Adapting Scrum to your culture' means making the necessary practice accommodations to your reality. One example might be that, instead of foregoing daily standups for distributed teams, have the remote team members phone or video-conference in to daily standups. Yes, this is not optimal. But the reality is that many companies do not have working environments that facilitate team productivity, and we can't ignore that or maybe even change it... initially.

In my classes, I have borrowed a phrase/mindset from David Anderson: instead of saying "No," say "Yes, with consequences." For instance, when attendees ask if they can have people work on work outside their sprint backlog, I reply, "Yes, with consequences... you will have to adjust your expected team velocity to reflect the reduced bandwidth and increased context switching."

So, if you're going to adopt Scrum, adopt it in its entirety, adhere to the principles, and adapt the practices to accommodate your environment. This is the least-disturbing way to start. And then, utilize inspect and adapt and be willing to try to change environmental factors that interfere with increasing velocity... one factor at a time so you can 'boil the frog' without him realizing it.