To be honest (and in retrospect also kind of unfortunately), I actively shied away from Astrid Lindgren's three Kalle Blomkvist novels when my grandparents presented the German translations (and where Kalle Blomkvist is called Kalle Blomquist) to me in 1978 as a gift. For even as a young reader I was not really into mysteries, and I therefore kind of assumed that Astrid Lindgren's Kalle Blomkvist would be too much like a Nancy Drew or an Encyclopedia Brown type of character (and thus rather textually annoying to and for me).
But yes, and after now having read the 2017 Susan Beard Oxford University Press translation of Mästerdetektiven Blomkvist (Astrid Lindgren's original 1946 Swedish text), after having both read and indeed and truly also quite enjoyed Master Detective: A Kalle Blomkvist Mystery, I definitely admit that I certainly made a bit of a mistake not considering the Kalle Blomkvist novels (in German translation) as an eleven year old. For while the mystery that Kalle and his friends solve in Master Detective: A Kalle Blomkvist Mystery is still a bit too much detective story oriented for me and that the villains and in particular Cousin Einar are rather too one-sided and as such somewhat annoying and even kind of creepy, I do very much and happily appreciate that unlike the above mentioned Nancy Drew and Encyclopedia Brown novels I read and totally did not like as a young reader, NOT EVERYTHING in Master Detective: A Kalle Blomkvist Mystery actually and automatically revolves around solving mysteries, and that much of Astrid Lindgren's text (and by extension also Susan Beard's translation) is thus a story of late 1940s Swedish childhood in a small town, is a story of friendship, fun and engaging escapades (including Kalle, Eva-Lotta and Anders playing harmless tricks on people, creating a circus performance for their neighbourhood and with two rival "gangs" of children engaging in extensive but actually rather good natured and friendly skirmishes), with the mystery of the jewel theft and Kalle Blomkvist and his two friends solving this and thereby also exposing Cousin Einar as a scoundrel being decently important but also not totally and utterly front and centre either.
And in fact, for me, with Master Detective: A Kalle Blomkvist Mystery, the close and easy, the natural friendship between Kalle, Anders and Eva-Lotta is what I consider truly first and foremost (and that this also nicely overshadows the mystery is indeed really delightful), with me absolutely adoring how Astrid Lindgren is showing three young teenagers who are very close friends, and that even with both Kalle and Anders obviously having a bit of a crush on Eva-Lotta, this does not ever interfere with Kalle, Anders and Eva-Lotta mostly being a wonderfully matched group of three (who have fun together, play pranks together and yes in Master Detective: A Kalle Blomkvist Mystery also play amateur detective and solve mysteries together). Highly recommended and a totally fun and engaging read, but yes, although I personally do majorly adore how in Master Detective: A Kalle Blomkvist Mystery Susan Beard uses all these typically and wonderful British expressions in her translation, I guess I should also leave a bit of a caveat regarding this (but that at the same time I equally do not really recommend the earlier 1950s Kalle Blomkvist English language translations by Herbert Antoine either, as his narrative flow is much less natural than Susan Beard's and that I also do not at all understand why in Antoine's renditions Kalle Blomkvist's name has been changed to Bill Bergson).