US tax implications for UK EMI (Enterprise Management Incentives)

I am a dual US/UK citizen, permanently resident in the UK.

I have a job offer which includes EMI (Enterprise Management Incentives), also known as share options.

As a US citizen, I have to file a US tax return. Please can someone explain the US tax implications/filing complexities of owning/exercising an EMI.

I should mention that the option is ‘currently valued at’ less than 10% of my salary, so it’s a nice perk, but not the biggest part of the deal.