If this book was by any other author I doubt it would work but David Mitchell has a certain elegance in his writing which stops you from giving up even if you get lost or bored. 
 The first part - of six (a sextet, Mitchell's love of this form shines brightly just as in 
 Cloud Atlas 
 ) - is narrated by a 15 year old girl called Holly Sykes who runs away in 1984 from home because her mother told her the boy she was in a relationship was no good, which was correct. The following four parts are narrated by people who are in her life at some point and each is narrated by those characters so in reading them your get different styles and voices which is brilliant as it switches genre from the likes of comedy to a dystopian future. 
 As much as I enjoy science fiction the section which focussed on that was my least favourite because it felt like it was dragging until a very quick conclusion. That, and the slightly random last part, was the reason I only gave it four stars. The first few parts were great; Hugo Lamb's chapter was my favourite as there was a lot in it such as romance, fight scenes and the use of an alias name by the undergraduate Cambridge student. 
 Others claim this is his finest book but I do not think it is a beautifully constructed as the likes of Cloud Atlas or 
 number9dream 
 although I kept track of it admittedly better than the latter. It is wonderful to read and revel in the use of language, each word is considered hugely to make it a joyous read.