Integer multiplication
There is a very clear explanation of the detailed implementation of sign extension in Booth-coded multipliers in the Appendix of Gary Bewick's 1994 PhD thesis (Stanford CSL-TR-94-617). The whole thesis is also available online.
For a more in-depth comparison of Wallace and Dadda trees (including an explanation of how each type of multiplier is constructed), please consult: Whitney J. Townsend, Earl E. Swartzlander Jr., Jacob A. Abraham, "A comparison of Dadda and Wallace multiplier delays," Proc. SPIE 5205, Advanced Signal Processing Algorithms, Architectures, and Implementations XIII, (24 December 2003); doi: 10.1117/12.507012.
Floating-point arithmetic
An essential read is Goldberg's article "What Every Computer Scientist Should know About Floating-Point Arithmetic" (ACM Computing Surveys, 23 (1), 5-48, 1991).