Alistair Moffat's latest idea is to imagine his way along the Highland Line, exploring history, geography, geology, language and culture as he goes.

It is a meander on both sides of the line and across disciplines and time. Unfortunately, an introduction by James Naughtie is not a particularly helpful send-off. He seems more concerned with making the case for north-east Scotland's exceptionalism (his own village in particular) than setting up Moffat's potentially fascinating quest.

The journey begins at Culloden and touches down there at regular intervals throughout the book. It is hard to say anything new about the breaking of the Highland clans at the battle and in its aftermath, and Moffat duly doesn't. However, he does set the tone for the rest of his journey, which, from the reader's perspective, is that of a brisk walk in the company of a knowledgeable companion interrupted by boxed passages highlighting things that are deemed interesting but tangential.

It is no surprise when one of these passages turns out to be a hagiography of John Prebble, who clearly inspired the Culloden content and was perhaps a more general inspiration in that he wrote "for the common reader" and has, "like much popular history, drawn the ire of academics".

This determined populism is both the strength and weakness of Moffat's book. Chapters range from the decidedly quirky to those where the author's impressive knowledge is on display. If, for instance, the connection between Islington Council and whisky, or whisky and men's eyeliner, is of interest then there's a chapter for that. By contrast, Moffat has expertise in the area of DNA research and ancestry and incorporates his knowledge into a rather impressive chapter on Moray.

Moffat's Highland Line is more excuse than theme. This need not be an issue, but becomes one when so many of the places it takes him are already well-trodden. Disappointingly, he has almost nothing to say about the contemporary situation. He remarks only in passing on the ubiquity of kilts obliterating whatever was left of a distinctive "Highland" dress, and it would have been interesting to have his take on the fact that children's Gaelic choirs are now almost as likely to be from Cumbernauld as from the Highlands. Where he does address the current position, it is only to confuse matters – declaring the likelihood that Gaelic will be a "dead language" at the end of the book having hailed Sahbal Mor Ostaig, the Gaelic College on Skye, as "an extraordinary achievement" at the beginning.

The Highland Line leaves one wishing for roads less travelled. Something, for instance, like Moffat's work on the Borders, published 10 years ago: dense, detailed, enlightening, yet eminently readable, and with six pages of "select" bibliography to the half-page here. It demonstrated that academic rigour and popularity are not necessarily opposites.