British English:
* ˈriː.dɪŋ (with the stress on the first syllable)
American English:
* ˈriː.dɪŋ (with the stress on the first syllable)
The pronunciation is essentially the same in both varieties of English. The "ea" in "Reading" is pronounced like the "ee" in "see" and the "ing" is pronounced like the "ing" in "sing".