How can I measure the usability of a catalogue?
In the past I worked on usability of interfaces in the information retrieval area, so I give you some practical ideas on how to measure the usability.

You didn't give details of what a "catalogue" is, so I will assume that a user has a problem (or need) and he is searching your catalogue (in paper or electronic format) for one or more solutions.

Then you can build a set of problems $P = \{p_1,...,p_n\}$, and for each problem a set $S^i$ of (possibly weighted) correct solutions: $S^i = \{ s^{i}_1,...,s^{i}_m\}$.

Then you can setup a test with real users.

Every user must solve all the problems in $P$ (in shuffled order) using your catalogue, in one of the two format (paper or electronic).

For each problem, you measure the time spent solving it. At the end you ask the users to give some judgements of satisfaction (using weighted values) on the two catalogues (covering different aspects of satisfaction, for example: "Do you think the catalogue helped you?", "Do you think it is easy to learn how to use it",  ....)

Then you can measure (and compare) the usability of the two catalogues in term of:


standard precision and recall of the results found for each problem $p_i$. Precision: number of correct solutions among the total number of answers; recall: number of correct solutions found among the total number of correct solutions in $S^i$
time spent for solving each problem $p_i$ (efficiency of the system);
user satisfaction


For what concerns the mapping between a paper catalogue to a system interface, you can "record" what users do during their searches on the paper catalogue, then try to "simulate" the actions of those users that performed better using an expert system (see expert system design).