I think there are a number of different strategies that Ishiguro uses in this wonderful book. Firstly, we can see that the central strategy he uses is raising our curiosity about these seemingly normal children. The strange world in which Kathy, Tommy and Ruth live is particularly bizarre, and it is a little while until we are able to fully understand what is actually going on and why they have to do various things, such as submit their best work to be viewed by somebody who clearly hates and despises them. We also wonder why they are so excited about being able to select things that are clearly the cast offs of other children. It is only slowly that Ishiguro reveals to us what is going on as we realise the truth about these children.
Secondly, and perhaps this is more of an annoyance than anything else, Ishiguro intrigues us as readers through presenting the clones as meekly accepting their fate. They make no effort to escape or to resist their destiny as clones who have to face multiple operations causing them great pain until they die. They almost act like robots rather than humans in the way that they face their fate unthinkingly and seem unable to contemplate any other way of life. This makes us ask profound questions about ourselves as humans and whether we too act like robots in certain ways or when confronted by certain situations. Just as the clones seem unable to ask the bigger questions that could lead them to change their fate, do we as humans do the same thing?