Tech recruiter here with 8 years of experience running a recruitment agency and I have seen 1000s of people negotiating salary (in Switzerland).

I wouldn't never recommend doing what the author suggests, namely: "I’d prefer to discuss the details of the offer over e-mail."

The phone is always better. Busy business people such as recruiters prefer it. Especially, because nowadays everyone hides behind text. Only the phone or an in person meeting gives you the chance to really hear what is possible compensation-wise and then really get what you want.

Btw I wrote this guide years ago: https://iwangulenko.gumroad.com/l/5-salary-negtiation-hacks?...