Unfortunately, it's in Swedish, a language I don't speak or read. I had assumed it would be in either English (the language of most of Tolkien's readership) or Danish (the author being a professor at the University of Copenhagen). So, here's hoping for an English translation.
In the meantime, if you're a completist not put off by not being able to read the books you collect (in which case you really shd have that Bulgarian biography of JRRT too), or if you can read Swedish (either from being a Renaissance Person or from belonging to the thriving and long-established Scandinavian Tolk folk), I'm told it's available from aritikvariat.net (http://www.antikvariat.net/get/search.cgi?post). At the least, the cover (a photo of Tolkien in front of an enlargement of Fimbulfambi's Map) looks good; I don't know if the other illos are previously unpublished or not.
For the original post I saw announcing the book, whose full title is TOLKIEN: MY FRIEND RONALD AND HIS WORLDS, see
There's also a brief interview with the author here (http://www.lotrplaza.com/forum/forum_posts.asp?TID=226514); scroll down to the twelfth message for it. Later in the same thread (the twenty-ninth message, I think) comes a table of contents listing of each chapter, which gives a good idea of the book's range, though not of course its flavor.
Given how much I enjoyed Zettersten's talk at the 2004 Marquette Tolkien Conference -- is it five years ago already? -- since published in THE LORD OF THE RINGS: SCHOLARSHIP IN HONOR OF RICHARD E. BLACKWELDER, I've been looking forward to this one. For one thing, Arne comes at it from a perspective no previous writer has enjoyed: a fellow expert in the AB language of the ANCRENE WISSE, the discovery of which was one of Tolkien's supreme scholarly accomplishments, though previous Tolkien scholars (myself included) have more or less ignored it, mainly I think through the lack of linguistic training necessary to properly evaluate and intelligently comment upon it.
If any Swedish-speaking reader has read it, I'd enjoy hearing his or her reaction/evaluation of the book.