Ms Tantchev has now reduced her "day job" in the public service down to three days a week to cope with the growth of the business, and Bookabuy will hire its first full-time employee in the coming months.
While it's still a tiny niche, the couple believe their 60 per cent year-on-year growth shows there's an appetite for a human, personalised touch, even in the face of Amazon's "similar purchase" recommendations.
Bookabuy customers pick from a subscription category such as modern fiction or young adult, provide a bit of information about the recipient's reading tastes — and Mel does the rest. If the customer is sent a book they already own, they can exchange it for a new one at no extra cost.
"Unlike a Netflix or AI-style personalisation, we hand-pick books," she said. "I do a lot of research. At least 30 to 40 per cent of my time is spent researching, the rest is placing the book orders and giftwrapping."
Mr Tantchev said the business was averaging 500 books per month.
"That tends to ebb and flow through the year, obviously gifting occasions and seasons are quite big, that's when the business expands significantly," he said.
"The key difference for us is the personalisation. You always know that when you get a Bookabuy subscription there's going to be that element of personal care, making sure it's always relevant."
He said while there had been "a lot of hoo-ha" about Amazon coming to Australia, it "hasn't really impacted us from a growth and revenue perspective".
"Also interesting is in America Amazon's trying a personalised book subscription service, similar to ours," he said.
While they haven't "crunched the numbers", the couple believe their customer churn rate is "quite low". "We've got people who are being gifted a subscription and when it ends people will sign up for themselves," Ms Tantchev said.
Mr Tantchev said he believed the business could scale, despite its hands-on nature.
"I don't think we feel constrained by the fact there is a manual element," he said. "We want to keep growing the business as fast as the last few years if not faster. We can always get additional hands to help, whether for selecting or wrapping books."
They also "want to try and get as intelligent as we can" by bringing in some sort of automation to assist with book selection, but "always with a person" making the decisions.
"Personalisation is the real passion behind what we do," he said. "The main driver behind Bookabuy has always been creating something special and creating a brand people can love."