Potato ,
I agree with KatieKaye and her replies are really good.
So, for context , I have a good degree in English Literature (not boasting because the things I am rubbish at are legion , you could not count them, they would run into the thousands ) but one thing I can do is read stuff and so I thought that I might be able to give you another view from the one you have had from your schooldays. One of my DCs is also dyslexic so I have some, albeit imperfect , understanding of that. I am not a teacher or a tutor, just a graduate from many years ago.
So just my thoughts are
- Do not think of a text as a particular level (as Castle said) . Eg you can study Jane Austen at GCSE or you could write a PHD thesis on her . The difference is the response and analysis.
- I think your friend has been very clever in recommending that short story to you . I have never read him before but did this afternoon so thank you , I believe it has been called something like a very nearly perfect example of a short story . The vocabulary and phrasing is not easy . I would say (pace KK) that if you want a similarly told short story (1st person narrator and an ending you need to think about , try The Snows of Killimajaro Ernest Hemingway (who I love - sorry KK ) ) Really really good short story .
3 . Decide what you want - do you want to appear well read or try out things you like ? No-one can read all the "classics " nor would they want to . What I utterly admire about you is giving things a shot. So for example , there are things about Dickens I like (can be funny , social comment etc ) but frankly if I never pick up another Dickens novel again it won't be a moment too soon. 
- One last thing , If you really want to improve your comprehension and missed out on some school stuff then an off the wall suggestion is - why not pick a text (e.g. A Streetcar Named Desire - Tennessee Williams ) order it from Amazon - you can buy it for 1p + p&p second hand and then order the York advanced notes for A streetcar (also v cheap (a few pence) 2nd hand ) These are explanatory notes made to investigate the text for school students - so not going to get you a Nobel Prize but if what you want is some aid in comprehension then I think a decent idea.
- Reading is for pleasure . Read anything that pleases you . If you like history then as KK says - read some historical fiction. It could be e.g. Georgette Heyer , or you could give Hilary Mantel a go (bit more difficult) , or
if you like mystery - yes I again

agree with KK that Agatha Raisin is a good, easy read , if you want to test yourself a bit more then try Agatha Christie - not too hard , and very good in the sense of plotting etc.
Anyway , gone on too long .
I really wish you well potato and do PM me if you think I can help .
CDL