Regioselectivity in Diels–Alder reaction between 2-nitrobuta-1,3-diene and acrylonitrile Since $\ce{-CN}$ shows strong −I effect, there will be δ+ charge on the carbon adjacent to it. Similarly, $\ce{-NO2}$ shows strong −I and –M effects. So, I proposed that π-electrons are being donated to the electron-deficient parts:

But the answer given in my book has $\ce{-CN}$ group at the third position to $\ce{-NO2}$ group. Can someone please tell me where I have got my concepts wrong?
You pointed out correctly that $-CN$ has a great $-I$ effect but it won't bring a $+\delta$ on adjacent carbon atom, reason being it's instability. Apply electromeric effects on propanenitrile. 

If you need help then just comment below :-)