Trying to figure out The Summer Book

Read thru the foreword to Tove Jansson's The Summer Book but didn't find much illumination there, either. Realized belatedly that in fact these scenes do comprise a single summer - the first scenes reference April (hard to believe that the young Sophia would go for a swim in the Baltic in April but so be it) and ends in August, as they prepare their summer house for the long, hard winter - in fact, stocking it rather handsomely as a refuge for any mariners who take shelter on the island - a beautiful Scandinavian tradition. In fact, the last chapter, with all the details of house arrangement, is one of the best in the collection. I'm struck though by how few of these chapters stay in my mind a day after completing the reading - is that just me or is there something elusive about these pieces? I keep trying to get my mind around the characters and their relationships. The intro correctly notes that a key sentence is one of the first stories is that Sophia has a bed to herself for the first time this summer bcz her mother died - what a fact to just slip in there and, much worse, never return to! It's of course like a shadow looming over the novel, and the failure to confront this sorrow is also very Scandinavian I think - being tough, stoic, reserved, and orderly are the key virtues - and then, usually, everything comes pouring out at once - like a ketchup bottle, someone once said - in a night of drinking. That doesn't happen in this "novel" - though there is some drinking. I have to say Jansson has no conception of how to establish Sophia's character; the intro says she's supposed to be 6 years old, and that how she seems at the start, but at other times she seems to be a teenager - or a ridiculously precocious 6-year-old. I don't know someone will have to explain this one to me.