The paper gives a systematic review of the basic ideas of (non-relativistic) quantum mechanics including all improvements that result from previous work of the authors. The aim is to show that the new theory is self-consistent and that it reproduces all measurable predictions of standard quantum mechanics. The most important improvements are: 1) A new realist interpretation of quantum mechanics assumes that all properties that are uniquely determined by preparations can be viewed as objective. These properties are then sufficient to justify the notion of quantum object. 2) Classical systems are defined as macroscopic quantum objects in states close to maximum entropy. For classical mechanics, new states of such kind are introduced, the so-called maximum-entropy packets, and shown to approximate classical dynamics better than Gaussian wave packets. 3) A new solution of quantum measurement problem is proposed for measurements that are performed on microsystems. First, it is assumed that readings of registration apparatuses are always signals from detectors. Second, an application of the cluster separability principle leads to a locality requirement on observables and to the key notion of separation status. Separation status of a microsystem is shown to change in preparation and registration processes. This gives preparation and registration new meaning and enhances the importance of these notions. Changes of separation status are alterations of kinematic description rather than some parts of dynamical trajectories and thus more radical than 'collapse of the wave function'. Standard quantum mechanics does not provide any information of how separation status changes run, hence new rules must be formulated. As an example of such a new rule, Beltrametti-Cassinelli-Lahti model of measurement is modified and shown then to satisfy both the probability-reproducibility and the objectification requirements.