A simple model of epitaxial growth proposed by Wolf and Villain is investigated using extensive computer simulations. We find an unexpectedly complex crossover behavior of the original model in both 1+1 and 2+1 dimensions. A crossover from the effective growth exponent β_ eff≈0.37 to β_ eff≈0.33 is observed in 1+1 dimensions, whereas additional crossovers, which we believe are to the scaling behavior of an Edwards--Wilkinson type, are observed in both 1+1 and 2+1 dimensions. Anomalous scaling

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... e to power--law growth of the average step height is found in 1+1 D, and also at short time and length scales in 2+1 D. The roughness exponents ζ_ eff^ c obtained from the height--height correlation functions in 1+1 D (≈3/4) and 2+1 D (≈2/3) cannot be simultaneously explained by any of the continuum equations proposed so far to describe epitaxial growth.