The first Tammy stories were written 15 years ago so there's plenty of history. Here's a catch-up that takes you to the start of Flying High:

Tammyverse Series Summary

Tammy (Tamara) Smart is a 21 year old student and businesswoman. Her father, an international merchant banker, retired to take care of her before she left St Andrews School in Thurso, Scotland. Her father remarried and she has two step sisters, Suzie and Angela.

Tammy has returned from protecting Royalty and is looking for a straightforward life as she's back at college with end of year exams. Naturally, however, that life isn't as simple as she'd like! Eventually, despite adversity, she does end up in the Isle of man for the TT Races (but you knew that if you've read Royal Retreat?)