Per https://twitter.com/marshray/status/255277780495917056 remove all mentions of PPTP as it as an unsecure protocol.
IMHO removing ALL references may be an error. Maybe leave a notice saying that it is an unsecure protocol?
Presumably this cos of the MS-CHAPv2 single DES break?
If so then it may be worth while mentioning that PEAP-MSCHAPv2 has the same problem with securing wireless networks, tho admittadly thats slightly drifting off topic from what i understand the point of the book to be.
Just to explain a bit more about this issue, this is the relevant blog post:
Please remove PPTP other than a warning of why not to use it and how to evaluate a VPN provider that offers it. If such a provider offers say, OpenVPN, IPSEC with certs and PPTP, the other solutions may be fine but that they offer it is probably a bad sign.
Clarify mentions of PPTP to discourage its use (solves issue #4)