The non-school books - are they worth the effort?

[tosomja.livejournal.com]

I read all the four school Marlow books as a child and absolutely loved them, read them 100s of times etc.  Now I have rediscovered them and realised only for the first time that there were others - I just thought that all the references to the holidays and falcons etc were things which happened 'off-stage', as it were.  So I acquired a version of the GGB Thuggery Affair, but found it really hard going and nothing like as good as the school books.  In fact I gave up once altogether, and then came back to it and managed to finish but wasn't hugely impressed..  I have also acquired The Ready Made Family which I enjoyed much more, but still, not as much as the school books. 
Given that it requires a fair amount of time and money to acquire the rarer Marlow books, it is really worth the struggle? Or are the school books the most popular for a reason?  What do you think - does anyone actually prefer the non-school books?   I don't want to spend a lot of effort on them only to wish that I'd kept to the school books and kept my memories of AF as good as they were!

And also what do you think of the historical ones? Are they as good, and do they connect to the later Marlows in any way apart from the characters being called Marlowe?