Don't know you are interested in P&R algorithm or tool.
For algorithm, Modern VLSI Design: System-on-Chip Design (3rd Edition) by Wayne Wolf has a very good chapter on this topic. Essential Electronic Design Automation (EDA) is another useful book for entry level. Then you might search IEEE papers for futher reading.
For tools, the best way is to practise demo while reading manual. Also do a Google Search. I think that will be much helpful.