MyISAM is fast at reads. You can use innodb for the transactional, writeable master, and replicate to MyISAM for read-only slaves. This also gives you full-text search.
InnoDB is faster at reads for most workloads on modern hardware. MyISAM has horrible scalability across multiple CPUs. MariaDB recently improved in MyISAM with the segmented key cache, but I haven't seen any results of head-to-head benchmarks since then.