The new book, Diagnostics for Experimental Thermonuclear Fusion Reactors 2, is a collection of papers presented at a second Workshop on the Diagnostics for ITER organized by the International School of Plasma Physics in Varenna, Italy in September 1997. With a gap of two years since the previous workshop there had been time for considerable refining and rethinking of the earlier ideas while some designs simply evolved and became more credible. One daunting aspect of this book is that it shows that the authors have often become more aware of the challenges that the ITER device present to diagnostic implementation while the demands of ITER plasma control needs and physics understanding have also become clearer. The book is in no way dated by its relationship to the full-sized ITER; the thought that has gone into these designs relates as well to a smaller device. The issues of integration of diagnostics onto smaller ports with possibly less shielding will have to be addressed but no significant problem is foreseen. Nor are any new plasma measurements likely to be required, but the dependence on advanced tokamak modes of performance may place tighter specifications on the measurement requirements for control, particularly on the spatial resolution of profile parameters such as the density, temperature and safety factor. The quality of the printed papers makes for very good reading, even though many of them concentrate on detailed design aspects of the interface of a diagnostic system with the structural material of the tokamak. Often the concerns are about maintenance of alignment, vacuum and window interfaces and, very much for the optical diagnostics, performance and lifetime of mirrors placed close behind the first wall. There is a wide variation between the progression in design of the diagnostics, but this is easily explained by the very different amounts of time that were spent on design of different systems. The organizers had been looking for a broad coverage of the systems required to enable an assessment of the overall status of this aspect of the ITER program, and this book provides that perspective. The initial set of papers about the device itself, the requirements on quality of measurement of a very large number of parameters and the overview of the ITER Diagnostic System as it stood in September 1997 provide a very interesting insight into the integration of plasma measurements into the whole framework of a large ignition device. An unusual aspect is the presentation of judgements made about the likely capability of some measurements being able to meet the requirements laid down and so leading to the need for further development in those areas. Design requirements for a divertor where the heat loads can be extreme are presented clearly and so is the issue of how to use many individual diagnostic instruments in the overall control of the plasma, a necessity for obtaining long, near-steady-state ignited plasmas. The design of the LIDAR Thomson scattering for measurement of the electron temperature and density profiles is the most advanced. Many design challenges have been overcome, and this design will be an important resource for designers of other optical systems with some similar problems. A unique issue for ITER diagnostic components close to the plasma is the impact, both prompt and lasting damage, caused by the high irradiation environment and the work to look at some aspects of this are reported here. Changes in conductivity for insulating ceramics and both absorption and luminescent effects in optical components such as fibreoptics must be taken into account in the selection of materials and their use in the design. Many of the design issues only become important in a reactor-prototype device such as ITER, but the solutions to many diagnostic engineering problems have relevance not only to the future reactor, but also to new diagnostic installations on today's devices. There is a caveat. This book is mostly devoted to the measurement requirements and the design detail necessary to achieve such goals. It is not for the student wanting to learn about the physical principles on which a diagnostic technique is based. There is very little about those principles but, in general, the referencing to relevant papers is quite good. Papers in the earlier volume often addressed the physics issues adequately.