This book gives an excellent overview and in-depth treatment of all aspects of bifurcation analysis in geomechanics. This is sophisticated and powerful technology, which can be exploited not only in petroleum engineering rock conditions but in many other geomechanical applications.What is the use of bifurcation analysis in petroleum engineering rock mechanics? This question no doubt will be asked by engineers working in this area with generally rather practical and application oriented portfolios. Is there any use at all, is it not just an academic subject, at best useful for wellcontrolled conditions such as those dealt with in structural engineering of surface facilities? Are subsurface rock conditions with inherent heterogeneity, anisotropy and layering not so uncertain that highly sophisticated numerical techniques with very precise determination of failure are out of balance? Many sceptics, amongst whom I have found myself for some time, look upon bifurcation analysis in that way. Until recently there was definitely no strong business pull from petroleum engineering to develop bifurcation analysis in geomechanics because no operating company was really asking for improved production performance. Application of bifurcation analysis to petroleum engineering was clearly a technology push; a technique that was available and was (and is) waiting for people seeing opportunities to apply it. Once these opportunities were found, this fine technology appears to be a lot more beneficial for our ‘rough’ business than initially anticipated. For instance, it allows us to solve the very important question of scale dependency of our rock mechanical tests, such as whether a hollow cylinder with a 8 mm hole can be representative for an 8??? wellbore. Transition between different borehole failure and stabilisation mechanisms can now be understood, which significantly increases the scope for barefoot completions and exclusion or postponement of sand control. Suddenly a technology that was initially regarded as rather academic contributes to millions of dollars savings.