I read this book as a kid when it first came out in the 80s. Came across these re-issued versions a few months ago so I'm reading them as she does too. They're basically an Irish Famous 5 style book about a few friends solving mysteries / crimes while on holidays. I really enjoyed it again (could be nostalgia) but my daughter who's 10 also enjoyed them. That's book 1 or 3 done.