Irrationality measures are given for the values of the series ∞ n=0 t n /W an+b , where a, b ∈ Z + , 1 ≤ b ≤ a, (a, b) = 1 and W n is a rational valued Fibonacci or Lucas form, satisfying a second order linear recurrence. In particular, we prove irrationality of all the numbers ∞ n=0